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Coiporation 


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..{4\ . 


UPON  THK  ELKCTKICAL  EXPKHIMKiNTS  TO  DETEKMINK 

THE  LO(!ATION  OF  THE  BULLET 
IN  THE  BODY  OF  THE  LATE  PKEalDENT  GAHFIELl); 

AND  UPON  * 

A  SUCCESSFUL  FORM  OF  INDUCTION  BALANCE 

FOR  THE  PAINLESS  DETECTION  OF  METALLIC  MASSES 

IN  THE  HUMAN  BODY.' 

By  Alex  AN  DEK  Graham  Bkll. 


(A  paper  reiul  iHifore   the  Ainericnu  AHMotriiitioti  for  the  Advaicement  of 
Soieuce,  Ht  the  Montreal  meeting,  AvigUHt,  1882.)  , 


4#-S':' 


Thk  Hiiujcci  of  my  preHetit  paper  rei-alli*  a  time  of  intense 
excitement  and  painful  8Usponse.  The  long,  weary  struggle 
with  the  untimely  death-wound — the  prolonged  suffering  borne 
BO  bravely  and  well  by  the  lamented  President  Garfield — 
nuist  still  be  fresh  in  every  rec-oUjction.  The  wln)le  world 
watched  by  his  bedside,  and  hopes  and  fears  tilled  every  pass- 
ing hour.  No  one  could  venture  to  predict  the  end  so  long  as 
the  position  of  the  bullet  remained  unknown.  The  bullet 
might  become  safely  encysted,  but,  on  the  other  hand,  recovery 
might  depend  upon  its  extraction.  The  search  with  knife  and 
probe  among  vital  and  sensitive  tissues  could  rut  be  otherwise 
than  painful  and  dangerous ;  and  the  thought  naturally  arose 
that  science  should  be  able  to  discover  some  less  barbarous 
method  of  exploration. 

Among  other  ideas'*  the  thonglit  occurred  that  the  bullet 
might  produce  some  sensible  effect  in  modifying  the  Held  of 

'  A  prelimiuiiry  uotic*!  relating  to  this  paper  was  publiHhed  in  the  Cmnpte* 
Bendwi  of  the  French  Academy  of  Sciences,  Oct.  24th,  1881. 
^  Hee  Appendix,  note  1. 


mmmmmmmiamititttliMKatL 


M 


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iiiiliictioii  III'  II  coil  Itroii^lit  iiimr  tlif>  ImmIj  of  tlm  I'l'eHult^nt,  ami 
tliiit  tilt)  Inciilily  of  t'iKt  liiillet  iiii<;lit  tliUH  In;  (lotfriniiUMl  with- 
out fliiiiffcr  to  tlif  |iHticiif  hikI  svitlioiit  puiii ;  for  it  ii*  well  known 
tliiit  iiidiu-tioii  Clin  Ix'  powcri'iillv  cxiu'tcii  tlirongli  the  linniHii 
l»o<ly  witlioiit  jtroiiuciiifjj  any  «e>iHation  wliatuvur. 

f'/inii  fill'  liiililiirinif  of  /inliii't'ioit, 

Tlic  infiniMic«!  tlmt  is  cxcrcincd  ii|)on  induction  l>y  nu-tallio. 
niassi's  lias  fornuKJ  tiic  snl»juc,t  of  tnnnnrous  ox]u'rinicntH  l»y  dif- 
ferent invoHtif^atoi'H ;  an<i  tlm  principle  of  liaiancing  the  offotttK 
of  induction  on  on(^  portion  of  a  (circuit  l»_v  oijual  and  opposite 
effects  j)rodnced  ii|)on  aiiotiier  portion  has  lieeii  utilized  in 
nearly  all  sncii  invcstij^atioiis. 

Tile  earliest  form  of  induction  Imlance  for  this  purpose  ap- 
pears to  have  heen  doviso<l  in  Germany  l>y  I'rof.  Dove,'  al»)ut 
the  year  IS41,  and  a  j^ood  dest-ription  of  it  in  the  Kn^lish  Ian-- 
jijuai^e  may  he  foimd  in  Do  la  Hive's  "  Treatise  on  Electricity," 
(18r>;i  edition,  vol.  I,  pp.  41S-4;?:{)2. 

Another  and  superior  urranj^ement  for  the  same  purjtose  is 
the  well-known  inilu(i!..n  l»alan(re  (»f  I'rof.  1).  E.  Ilnghes'. 

The  Stati<'  Induction  Balance  of  J.  E.  II,  (iordon*  thoufj;h 
j)rimarily  intended  for  e.\p(M"inu^nts  upon  spei  itic  inductive  ca- 
pacity, might  also,  perhaps,  he  employed  in  the  same  class  of 
investifintioiis. 

My  own  atteniion  was  directed  to  the  Italancang  of  induction 
a  nmni>er  of  years  ago  Ity  the  disturhing  noises  produced  in  the 
t('lej>lione  Ity  the  opiiration  (tf  telegraphic  instruments  upon 
lines  running  near  the  teleplnuie  conductor. 

The  ditticulty  was  remedied  hy  using  two  (ronduetors  instead 
of  one,  and  hy  so  arranging  them  with  referenee  to  the  disturh- 
ing  wires  that  the  currents  indiuied  in  one  of  the  telephone 
condu(!tors  were  exactly  e«|ual  and  opposite  to  those  induced  in 

'  P(>KK-  Ann.  vol.  liv,  pp.  HOr)  WXt. 

^  A  Hiiiiilikr  aiipuralviH  wiut  independently  devised  in  Anierioti  li  number  of 
yt'iirH  ago  hy  Prof.  Rowlund,  <»f  Jolms  Hojikins  UniverHity.  It  it*  to  he  re- 
gretted thut  liiH  diBcovery  of  the  fact  that  he  Lad  lieen  anticipated  liy  Dove 
prevente<l  Prof.  Rowland  from  completing  and  publishing  his  reseiU'ches. 

"Phil.  Mag.,  July,  1879,  vol.  ii,  p.  50. 

*  Phil.  TrauB.  for  187'J,  p.  417, 


L 


tlio  other.  In  thiw  way  an  iii«lnrfion  ItalaiHtu  w»a*  f/nMlnccil 
«  m1  a  (|iiiot  circuit  sccin'tMl  fur  trlcplioiiic  purp*  net*.  This 
imithix!  wan  patmitud  in  En^huid  in  Novcinlmr,  IS?',  and  (hir- 
ing,'; the  wliohs  wintor  (tf  1877-H  I  was  un<ja};i!<i  in  London  np<»n 
t!.\pt»rinuintrt  ri»latin>^  to  th«  Hulijoc^t. 

In  tlio  »!onivci  of  thoso  riw<«ar(!liert  I  niadu  frtM|iHMit  nsc  of  tint 
Hpiralu  of  iiirtnhitcd  wiro,  liko  tliosc  (MnploytMl  i>y  tiie  hkto  Prof. 
Ilonry'  in  iiis  uxpurininntH  upon  induction. 

My  niotliod  waH  to  paws  a  rapidly  intorrupt(Ml  voltai<t  current 
througii  one  Hat  npiral  while  I  examined  its  field  of  in(hiction 
l>y  nieauK  of  anotiii^'  flat  spiral  contK^ited  with  a  telephone. 
The  c.urrentH  induceil  in  the  latter  coil  produ(^ed  a  musical 
tone  from  the  telephone. 

At  every  point  in  the  field  of  induction  it  was  found  that  i»y 
turning  the  plane  of  the  exploring  coil  a  position  of  silence 
couhl  lie  olitained,  and  another  of  maxinnnn  sound,  the  two 
positions  making  a  right  angle  with  one  another. 

It  was  also  noticed  that  when  a  position  of  silence  was  estah- 
lished  a  piece  of  metal  hrought  within  the  liehl  of  iiuluctioii 
eause<l  the  teleplmne  to  sound.  This  effei^t  was  most  marked 
when  the  two  Hat  spirals  were  in  chtne  proximity,  and  were 
arranged  with  their  planes  parallel,  as  kIiowii  in  Fig.  1. 

When  a  silver  coin,  such  as  a  half-<;rown  or  Horin,  was  passed 
acroHB  the  ^ace  of  the  two  coils,  the  silence  of  the  telephone 
was  hroken  three  times.  The  instrument  emitted  a  imisical 
tone  when  the  metallic,  disk  passed  the  points  marked  1,  2,  and 


JH^.!. 


\f\f\J\S\PC^  -3 


3  in  the  illustration,  hut  the  loudest  effect  was  produced  when 
the  coin  crossed  the  area  marked  "  2,"  where  the  two  coils 
overlapped. 

After  my  return  to  America   I  emimdied  these  and  other 
results  in  a  paper  "  Upon  New  Methods  of  Exploring  the  Field 

'  Silliiimn'B  Joumtil,  xxviii,  329;  xxxviii,  209;  xli,  117. 


iMHiii 


r 


of  Indnctron  of  Flat  Spirals,''^  whicli  was  read  before   this 
association  at  the  Saratoga  meeting  in  Angnst,  1879. 

Prtictical  Application. 

While  brooding  over  tlie  prol»leni  of  tlie  detection  of  the 
hnllet  in  tlie  body  of  Presid»^nt  Garfield,  tlmne  experiiuenta 
made  in  England  returned  vividly  to  my  mind.  It  seemed  to 
me  that  ir  the  overlapping  area  "  2"  of  the  two  coils  shown  in 
Kig.  I  conld  be  ])roiight  ovei*  the  seat  of  the  bullet  without 
disturl)ing  the  relative  positions  of  the  coils,  the  teleplume 
would  probaldy  amionnce  tlie  presence  of  tiie  bullet  by  an 
audible  sound. 

A  crude  expc  nient  was  at  once  made  to  test  the  idea.  A 
large,  single-polj  electro-magnet  (the  core  of  which  was  com- 
posed of  a  bundle  of  tine  iron  wires)  wat;  used  in  place  of  co.U 
A  (Fig.  1 ;)  and  a  small  coil  of  tine  wire  taken  from  a  hand 
telephone  was  arranged  a  little  to  one  side  of  the  pole  to  rep- 
resent coil  IJ.  The  snudl  coil  being  coimected  with  a  telephone, 
a  battery  current  was  passed  through  the  coil  of  the  electro" 
magnet,  and  the  battery  circuit  was  nmde  and  broken  by  an 
assistant. 

Under  these  circunnstances  a  much  better  balance  was 
obtained  than  could  possiidy  have  lieen  anticipated.  Upon  now 
i)ringing  a  leaden  bullet  near  the  sniidl  coil,  a  distinct  ticking 
sound  could  l)e  heard  from  the  telephone  each  time  the  battery 
circuit  was  made  and  broken. 

Being  absent  from  my  laiwatory,  and  without  facilities  for 
proper  experiment,  I  conununicated  my  i'?';as  to  Mr.  </harle8 
Williams,  Jr.,  of  Boston,  manufacturer  of  electrical  and  'ele- 
phonic  apparatus,  who  kindly  placed  the  resources  of  his  large 
establishment  at  ray  service ;  and,  at  great  personal  inconve- 
nience, delegated  his  best  workmen  to  attend  to  my  experiments. 

Upon  attempting  tii  devise  an  appropriate  form  of  apparatus 
for  the  special  purpose  in  view  I  saw  tiiat  there  were  great 
practical  difficulties  in  the  way  of  utilizing  the  arrangement 
shown  in  Fig  1,  and  it  occurred  to  me  that  the  apparatus  of 
Prof.  Hughes  might  perhaps  be  employed  with  more  advantage 
as  the  basis  of  my  experiments.     In  tJ-o  ordinary  form  of 


jfore   this 


ion  of  the 
pcriuients 
seemed  to 
»  shown  in 
Bt  without 
telephone 
llet  by  an 

J  idea.  A 
I  was  corn- 
ice of  coil 
>m  a  hand 
ole  to  rep- 
telephone, 
he  electro" 
ken   by  an 

ilance    was 

Upon  now 

net  ticking 

tho  battery 

acilities  for 
tir.  Oharles 
fil  and  "^le- 
»f  his  large 
al  iiu;oiive- 
xperitnents. 
f  apparatus 
were  great 
rrangeiuent 
pparatus  of 
a  advantage 
ry  form  of 


Hughes'  induction  balane<i  four  coils  are  used,  as  shown  in  Fig.  2. 
Through  the  agency  of  a  Hughes  microphone  the  ticking  of  a 
clock  is  made  to  create  an  electrical  disturbance  in  the  voltaic 


^y.  s. 


circuit  containing  the  two  primary  coils  (  A.  O)  and  a  corre- 
sponding disturbance  is  produced  by  induction  in  the  two 
secondary  coils  (B  D)  (!onnect<id  with  the  telephone.  If  the 
connections  are  so  arranged  that  the  currents  induced  in  the 
telephone  (nrcuit  by  the  coils  A  C  are  in  the  same  direction, 
the  ticking  of  the  clock  is  heard  very  plainly,  but  if  they  are 
in  opposite  directions  no  sound  is  perceived. 

In  the  latter  case  the  action  of  one  primary  coil  (A)  opposes 
that  of  the  other,  (C,)  and  an  electrical  balance  results.  If 
now  a  piece  of  metal  is  brought  near  one  pair  of  coils  (say  A 
B)  the  balance  is  disturbed  and  the  ticiking  of  the  clock  is 
audible  at  the  telephone.  The  arrangement  of  the  coils  (A, 
B,  C,  D)  was  the  point  to  be  studied,  the  microphone  attach- 
tnent  being  of  no  importance  in  the  combination ;  for  it  is  well 
known  that  a  rheotome  to  break  the  primary  circuit  completely  at 
intervals  can  be  substituted  for  tiie  microphone  with  advantage. 

It  seemed  to  me  that  two  of  the  coils  (A  B)  in  the  Hughes 
inducti(m  balance  might  be  attached  rigidly  to  a  wooden  handle, 
so  as  to  l)e  moved  over  the  seat  of  the  bullet  without  cha.iging 
their  relative  positions,  and  that  all  the  adjustments  necessary 
might  be  made  on  the  other  pair  of  coils,  which  need  not  he 
moved  from  their  place,  and  would  not  therefore  be  liable  to 
disarrangement.  If  a  single  pair  of  coils  were  to  be  used  as  in 
Fig.  1,  they  must  be  adjustable  one  upf»n  the  other.  But  if  dur- 
ing the  course  of  exploration  the  coil  B  (Fig.  1)  should    le 


moved  from  its  propor  poHition  even  to  the  extent  only  of  a 
smtiU  fraction  of  a  millimetre,  the  halance  would  l»e  dirtturhed 
and  the  exploration  mi<rht  have  to  he  stopped  in  ->rder  to  ad- 
just the  apparatus.  These  consi'Uirations  led  me  to  the  eonelii- 
sion  that  some  moditieation  of  the  Hughes  inchietion  l)alance 
was  most  suitable  for  my  purpose,  and  I  inunediately  com- 
mencied  the  eonstruction  of  iiueii  an  apparatus. 

Si/(/f/eKfloitN   Tested. 

Just  at  this  time  I  learned  from  the  newspapers  that  Prof. 
Simon  Neweond),  of  Wasliington,  had  tlie  i<lea  of  using  a  u«ag- 
netic  needle  to  indicate  hy  retardation  of  its  rotation  the  pnjx- 
inuty  of  the  huUet  in  the  body  of  the  President,  and  \  tele- 
«rrapiied  to  Prof.  New(rond>  the  ofPer  of  my  assistance  in  carry- 
ing on  experiments,  knowing  t!»e  comparative  ditttculty  he 
woidd  experience  in  having  apparatus  made  in  Wasiiington. 

At  Ins  suggestion  I  tested  tlie  point  whether  the  rotation  of 
a  leaden  disk  and  of  a  leaden  huUet  underneath  a  delicately  sus- 
pended magnetic  needle  would  cause  a  deflection  of  the  needle. 

The  disk  ocx^asioned  a  deflection,  but  the  btdlet  produced  no 
sensilde  effect.  I  telegraphed  the  result  to  Prof.  New(!ond», 
and  at  the  same  time  took  occasion  to  inform  him  of  tha  hope- 
ful results  I  had  obtained  witii  tlie  <!rudely  constructed  indiur- 
tion  balance  referred,  to  above. 

r  wasnnich  gratified  by  his  immediate  appreciation  of  theex- 
l  jriment.  lie  telegraphed  that  he  thought  an  induction  l)alance 
promised  a  nuich  more  hopeful  solution  of  the  proldem  than 
his  own  metiiod,  and  -incouraged  me  in  every  way  to  contimie 
my  experiments. 

This  appreciatioii  determined  me  to  proceed  to  my  lal>oratory 
at  Washington,  where  I  was  accompanied  by  Mr.  Sunnier 
Tainter,  who  wis  anxious  to  assist  in  such  a  cause.  I  learned 
from  Prof.  Newcomb  that  Mr.  Geo.  M.  Hopkins,  of  Brook- 
lyn, had  independently  suggested  the  use  of  Hughes'  induc- 
tion l)alance,  and  had  ma<le  experiments  in  BrmAlyn,  the  results 
of  whicii  were  p\d dished  in  the  New  York  Tribune  (m  the  11th 
of  July,  1881.'      Mr.  J.  Stanley  Brown   (private  secretary  of 

'  See  Appeuilix,  m)te  2. 


PreHuleut  ClarfieM)  kindly  luinded  to  me  the  letters  lie  had  re- 
ceived t'roin  Mr.  Hopkins,'  nnd  also  a  Ilu}j;hes  induction  hal- 
anj.ii  like  that  shown  in  Fig.  2,  whieh  Mr,  Hopkins  had  forwarded 
to  the  Executive  Mansion  for  trial. 

Tills  apparatus  was  at  on(!0  tested  in  my  lal)oratory,  with  re- 
sults slightly  better  than  those  1  had  ohtainc-d  in  Boston. 

My  li(»ston  apparatus  did  not  give  a  greater  hearing  dis- 
tamie  than  3  em.,  wiiereas  with  the  Hopkins  apparatus  I  «M»uld 
distinguish  effec^ts  at  a  distance  of  .'{.75  cm. 

Two  of  Mr.  Hopkins'  coil.^  (A  H,  Fig.  ii)  were  then  fas- 
tened upon  a  wooden  handle  to  form  an  exploring  instrument, 
and  the  whole  apparatus  was  -irranged  for  imtnediate  use  in 
(itise  of  any  necessity  ai-ising  for  an  experiment  upon  tlie  Pres- 
ident, r  set  myself  in  comniunic^ation  witli  Mr.  Hopkins,  and 
requested  his  assistance  and  co-operation,  and  in  reply  re<'eived 
through  Private  BecTetiiry  Brown  tlu^  following  account  of 
further  experiments : 


"  t)0  Irving  Pi.aok,  Brooklyn,  July  10,  1881. 

"  Mr.  J.  Stani,fa-  Brown  : 

"  DioAR  Sir  :  [  have  made  tw(j  ne  .v  instruments  on  plans  differ- 
"  ing  from  that  sent,  hut  they  yield  no  better  results.  Tlie  first 
"  <;onsisted  of  ^^  j 

"  two  oblong 
"coils  a  r  - 
"ranged  at 
"  right  angles  soim^^ 
"  to  each  oth- 
"  er,  tlius  : 


"The  outer  coil  being  of  coarse  wire  (No.  18)  placed  in  the 
"  primary  circuit,  the  in.ier  coil  being  of  very  tine  wire  (No. 
"  36)  and  connected  with  a  telephone.  The  parallel  currents 
"  traversing  the  wires  neutralized  each  other,  and  no  audii»le 
"  efPects  are  perceived  in  the  telephone,  but  on  presenting  a 
"  metallic  body  to  tlie  instrnment  upon  a  line  l»isecting  the 
"  angle  between  the  coils  the  clicking  in  the  telephone  is  heard. 

"This  histrument  possesses  only  one  advantage  over  that 
"  sent,  and  that  is  that  it  requires  no  adjustment. 

'  See  Appendix,  notes  .  uud  4. 


■i 


8 

"  The  other  instrument,  (ronsists  of  two  hirge  coils  of  very 
"  tine,  wire  (No.  ;^<))  phiw/l  upon  opposite  sidei*  of  a  coil  of 
"  eoarne  wire,  (No.  16,)  the  tine  coil  heinu;  connected  ho  that 
''  the  induced  cin-rents  neutralize  em-h  other,  thus: 


nff.d 


Ihtmrrupter. 


"  I  am  sorry  to  he  ohli<;ed  to  say  of  this  as  of  the  other,  that 
"  it  is  no  more  sensitive  tlian  the  one  sent.  To  produce  the 
"  best  effects  from  the  instrument  which  you  have  it  will  be 
"  ne<!essary  to  use  all  tlie  l)attery  power  p()ssil)le  witiiout  burn- 
"  mg  the  coils,  and  two  receiving  telephones  of  the  best  con- 
"  struction  ir.ust  be  used. 

"  As  I  stated  in  the  iirst  instance,  if  the  ball  is  more  than 
"  two  inches  deep,  I  think  it  cannot  l)e  located  l>y  this  means. 

"  If  larger  coils  were  used  the  instrument  might  be  operative 
"  at  a  greater  distaiu*,  but  the  area  indicated  as  containing  the 
"  ball  would  be  so  large  that  the  result  would  be  indefinite  and 
"  without  value. 

"  Hoping  that  Prof.  Bell  will  be  aide  to  succeed,  I  remain, 
"  Yours  very  truly, 

"Geo.  M.  Hopkins." 

Prof.  Hughes  of  London-  England,  Prof.  Trowbridge  of 
Harvard  College,  Prof.  Rowland  of  Johns  Hopkins  University, 
and  other  authorities  were  consulted  by  telegraph  as  to  the  best 
theoretical  form  of  induction  balance  for  the  purpose  re([>iiied, 
while  empirical  experiments  were  being  carried  on  under  my 
direction  in  my  laboratory  at  Washington  l»y  Mr.  Sumner 
Tainter ;  in  the  electrical  work -shop  of  Davis  and  Watts,  in 
Baltimore,  l»y  Mr.  J.  H.  C  Watts,  and  in  the  estaldishment  of 
Mr.  Chas.  Williams,  Jr.,  in  Boston,  by  Mr.  Thomas  A.  Gleason. 
To  test  the  influence  of  size  of  coil  an  instrument  was  (;on- 
etr\icted  in  which  the  coils  were  no  larger  than  the  bullet  for 
which  we  sought,  (as  had  been  suggested  by  Prof.  New(!omb,)» 
and  experiments  were  also  made  with  the  enormous  coils  used 
by  the  late  Prof.  Henry  in  his  researches  upon  induction,  which 

•  See  Appeudix,  note  5. 


7J>  primary  cotla  of 

y'truUtct-itm  balance. 


§ 

were  kindly  lent  to  me  for  the  purpose  l)y  the  Sir.ithrtotiiiin  Tii- 
Htih.tioii,  l»ut  neither  the  small  nor  the  large  coils  produced  more 
Hatisfactory  resultH  than  those  we  had  already  ol)tained. 

To  test  battery  power,  20  enormous  Bunsen  elements,  which 
had  formerly  been  used  to  light  the  gas  at  the  (Capitol,  were 
placed  at  my  disposal  l»y  Mr.  Rogers,  electrician  of  the  Capitol, 
but  while  great  elec^tro-motive  forc^e  was  evidently  of  use  we 
derived  no  advantage  from  such  a  l)attery  as  this. 

To  test  the  influence  of  speed  of  interruption,  Mr.  Marean, 
Supt.  of  tlie  Western  Union  Telegraph  Co.  in  Washington, 
kindly  lent  us  an  electric  motor,  by  means  of  which  we  were 
able,  with  the  aid  of  a  rotating  commutator,  to  obtain  inter- 
ruptions of  the  primary  circuit  of  all  rates  up  to  600  interrup- 
tions per  second,!  and  we  . 
found  that  the  more  rapid  Ftffo. 
the  rate  of  interruption  the 
more  distinct  was  the  sound 
in  the  telephone.  The 
hearing  distance,  however, 
was  not  proportioiuitely 
increased.  The  automatic 
interrupter,  (shown  in  Fig. 
5,)  yielding  about  100  in- 
terruptions per  second, 
gave  as  good  results  as  any, 
and  was  nuich  more  conve- 
nient. This  interrupter 
was  therefore  afterwards 
used  exclusively  in  our  ex- 
periments. 

The  theoretical  form  of  coil  suggested  by  Pi'of.  John  Trow- 
bridge? was  substantially  the  same  as  that  proposed  by  Prof. 
Rowland,'"  and  is  shown  in  Fig.  6. 

The  arrangement  was  quite  sensitive  to  metal  placied  in  the 

•  Mr.  8uiuner  Tninter  has  since  made  nn  upparattis  operating  in  a  similar 
manner  by  means  of  which  he  Las  obtained  as  many  as  4,000  interruptions  of 
the  circuit  per  second.  • 

'^  See  Appendix,  note  G. 

'  See  Appendix,  note  7. 


10 

interior  of  the  coil,  hut  the  heiiriii^  distiince  for  a  Imllct  exter- 
luil  to  tlie  i!<»il«  was  no  greater  than  hefore.' 


Prof.  IIuijheH*  proposed  to  have  two  flat  superposed  coils 
wound  on  a  single  reel,  so  that  the  two  coils  shonid  form  a  sin- 
gle one  as  regards  their  relative  distance  ;  and  Mr.  F.  T.  Bic^k- 
ford,  Washington  correspondent  of  tlie  New  Voi-k  Trihune, 
suggested  winding  two  wires  side  l)y  side  into  a  single  coil,  so 
that  the  relative  distances  of  the  wires  from  the  Itullet  should 
be  a'osohitely  the  same.  Mr.  Chas.  E.  Bnell''  and  Dr.  Chi- 
chester A.  Bell'  proposed  to  determine  the  depth  of  the  l)ullet 
beneath  the  surface  by  causing  a  similar  bullet  to  approach  the 
i)alancing  coils  until  silence  was  restored  ;  the  secondary  bullet 
it  was  presumed  would  then  l»e  at  the  same  distance  from  the 
balaiu'ing  coils  as  the  embedded  bullet  from  the  exploring  coils. 

The  results  of  all  the  experiments  so  far  nuide  were  unsatis- 
factory. I  had  tried  every  thing  that  had  been  suggested,  but 
4  (!m.  renuiined  the  extreme  limit  of  audil>ility  for  a  bullet 
like  that  whicli  IumI  struck  the  President.  Even  when  such  a 
bullet  was  flatttMied  by  being  flred  against  a  i)oard,  and  was 
presented  with  its  flat  side  towards  the  coils  of  the  explorer — 
the  most  favorable  mode  of  presentation — no  better  result  was 
obtained. 

'  The  bnlauoo  (>1)titine(1  wiw  uot  ijuito  perfect,  iind  we  Imve  since  discovereil 
thnt  the  iuHtiliitiou  of  the  wires  of  oue  of  the  seeoudury  coils  wiw  defective. 
^  Hee  A])peudix,  iu)te  K. 
'  See  Appeudix,  note  0. 
^  See  Appendix,  note  10. 


(52SSi*i»w 


JVff.r. 


11 

Oriyhial  Kj'jhrriinentK. 

In  the  theoretical  arrimjijeiMent  recomineiided  by  Profs, 
Trowhridge  and  Rowland  (Fig.  6)  the  primary  coil  A  was  of 
finialler  diameter  tlipti  tlie  secondary  B.  This  had  given  lis  no 
better  effects  than  the  ordinary  form  of  Hughes'  balance,  (see 
Fig.  2,)  in  whicli  the  two  coils  A  B  were  of  erjual  diameter. 
We  then  tried  tlie  effect  of  making  the  primary  (^oil  A  of 
greater  diametei  tlian  the 
secondary  B,  (see  Fig.  7,) 
and  in  this  case  we  ap- 
peared to  f»btain  an  in- 
crease of  hearing  distance. 
Five  centimetres  (2  inch- 
es) was,  iiowever,  the  ut- 
most limit  reached,  wlien, 
on  the  19th  of  Jul  .  Mr. 
J.  Stanley  Brown  and 
Dr.  Woodward  visited  my 
laboratory  and  witnessed 
some  experiments.  No  difficulty  was  experieiuied  in  detecting 
a  l)ullet  held  in  the  mouth  by  passing  the  exploring  c(nl  over 
the<-heek;  and  the  presence  of  a  ffattened  bullet  hehl  in  the 
(denched  hand  was  also  readily  determined.  Dr.  Bliss,  Dr. 
Iiey])urn,  and  Siu-geon-General  Barnes  visited  the  laboratory 
next  day  and  t^xpressed  tliemselves  as  very  hopefully  impressed 
by  the  experiments.  These  were  subsequently  repeated  in  the 
sui'geon's  room  at  the  Executive  Mansion  for  the  information 
of  Dr.  Frank  Hamilton  and  Dr.  Agnew,  who  also  seemed 
favorai)ly  impressed. 

Such  opinions  from  the  surgeons  in  attendance  upon  the  Presi- 
dent, and  the  continued  interest  shown  by  Prof.  Nawcomb, 
encourage<i  me  to  proceed  v'th  tlie  experiments.  > 

It  was  now  determined  to  test  the  effect  of  each  (involution 
of  the  primary  coil,  so  as  to  arrive  smpirically  at  some  idea  of 

'  I  desire  Hpecially  to  express  my  grati  ,nde  to  Dr.  Frank  Haniiitou  for 
words  of  eucourageraent  spoken  at  a  later  date  when  sympathy  and  encour- 
agement were  greatly  needed. 


jT^ 


■\j 


«" 


iMiaiiiiwiaf'.wu'.M-ag.!Wtji 


18 


the  bewt  shape  of  c<n\.  For  thin  purpoHO  Mr.  Tainter  con- 
HtnictiMl  the  iiixtniinents  hIiowii  in  Fijj.  H.  (^irtMihir  fj^ronvenwere 
tiirniMl  ill  two  hoarlw,  one  of  whiirh  is  shown  in  perspe«!tive  at 
A  and  tiio  other  in  section  at  I).  An  insiihited  copper  wire 
eonld  i)e  pressed  into  any  of  these  grooves  so  as  t(»  give  tlie 
wire  an  exuctly  circnhir  sliaj)e  of  i<nown  diameter,  and  the  two 
ends  were  passed  tiirougii  an  oritiee  in  tiie  Itack  of  t)ie  hoard, 
making  eomiection  with  a  simihir  ring  of  wire  in  tiie  other  in- 
strument as  sliown.  A  small  secondary  coil  (I  of  tine  wire, 
which  coidd  he  moved  witli  moderate  friction  n}>.in  the  Imri-  . 
zontal  rod,  was  coniuM^ted  to  another  similar  coil,  (E,)  and  to 
a  telephone ;  and  a  small  brass  ring,  (C,)  which  couhl  also  he 
moved  along  the  horizontal  rod,  was  used  instead  of  a  bullet 
to  disturb  the  balance. 

In  making  an  experiment  with  this  apparatus  the  secondary 
coil  (B)  was  first  placed  within  the  primary  ring  and  in  the 
same  plane  with  it,  and  the  l)alancing  coil  E  was  adjusted  to 
produce  silence.  T'le  brass  ring  C  was  then  moved  along  the 
horizontal  rod  until  the  balance  was  sensilily  disturbed  and  the 
relative  distances  of  the  (toils  and  the  brass  ring  were  noted. 

('ontiniiing  the  experiment  the  coil  B  was  moved  a  deter- 
mined distance  beytmc'.  the  plane  of  A,  and  the  balancing  coils 
again  adjusted  to  silence.  The  brass  ring  C  was  once  more 
caused  to  disturb  the  balance,  and  the  new  hearing  distance  was 
noted.  The  following  are  the  tabulated  results  of  a  series  of 
experiments  made  on  the  19th  of  July,  1881.  The  battery 
employed  consisted  of  six  bichromate  cells  connected  in  series. 


.W.- 


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Therto  figures  show  that  the  ilidanee  from  the  primary  coil 
A  (Fig,  8)  at  which  the  influence  of  the  hram  ring  C  hecamojwi- 
ceptible  ineream/  with  tJu;  diameter  of  the  primary  riny^ind  that 
them-omlary  coil  B  required  to  he  projected  amsidenddy  beyond 
the  plane  of  the  primary  in  order  to  obtain  the  maximum  effect. 

Tlie  conclusion  seemed  a  natural  one  that  the  degree  of  pro- 
jection A  H  of  the  secondary  coil  should  proportionally 
increase  with  the  diameter  of  the  primary  ring,  but  the  tabu 
lated  figures  did  not  fully  justify  the  inference. 

Tlie  experiments  had  necessarily  occupied  a  considerable 
time,  and  I  thought  that  the  difference  between  the  results 
that  shotdd  have  been  observed,  accordhig  to  the  above  hypoth- 
esis, and  those  that  were  a(;tually  ()l>tained,  might  have  been 
due  to  the  gradual  exhaustion  of  the  l>i<:hromate  battery  em- 
ployed and  to  its  polarization,  although  every  oare  had  been 
taken  to  preserve  its  power  by  removing  the  carbon  and  zinc 
plates  from  the  solution,  excepting  when  an  observation  was 


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made.  To  \mi  wluitlmr  tho  biittory  cxortod  iiiiy  nuiterial  inflii- 
oiicn  iipoii  tlu  Imiirin;;  (iistiiiifts  u  fiirtlicr  nerius  of  nxporiinentH 
WHS  miult!  witli  \\\v  Kiiiiu!  !»iittory. 

It  will  Ik)  rt»;oii  \)\  refurouct)  to  tliu  tnlmluteil  KtHtoiimnt  hIiowii 
above  t!  at  tlio  inaxiiinun  heariiijj;  (liHtaiu'c  H  ('  had  1k.;)Ii  oI»- 
taiiied  with  a  primary  riiij,'  ll.;5  cm.  in  diamoter  when  the  diw- 
taiire  A  H  lietweeii  tii(!  |)riiiiarv  and  Hecoiidary  v\nU  was  ouo 
(•('titiiiK'trc.  This  Hrraiijii'iiifiit  of  the  apparatuw  was  tlierefore 
adopttnl  tliroii^hoiit  the  foHowiiijj;  experiments: 

MeariiiK  diNtunce 

1.  ApiMinitiiNtrifil  with  1  cell.  (WchrniimtebivttBry)...(B(!,  FiK-H)  ^  It      uiiii. 

2.  Six  fi'llH  in  Ht-rifH..... (Hd.  Fig-M)  =1(>     mm. 

3.  Mix  ells  in  miiltiiilr  iirc (BO,  FiK.H)=    '.»     mm. 

4.  Hix  ct'll  in  two  HcricHof  3  eiich (H(!,  Fig.H)  -=  !">      mm. 

5.  Hiinu'  ixiicrimtnt  rii«Mktf<l (BO,  Fij{.H)  =13.5,nim. 

(1.  Siimi^  nxpurinit-nt  ropmiUMl  hy  Mr.  Tiiintcr (BO,  Fig. H)  -=12.5  mm. 

These  experiments  prove  1  tliaf  l>attery  power  diil  exert  an 
iiitliience  npoii  lieariti}.^  distance,  and  also  that  the  battery  in 
nse  was  irnwhially  deteri<)ratinf;. 

I  (•onchided,  therefore,  that    If   tlie  liattery  power  had  re- 
mained constant,  yKy.tf. 
the  hearing  distance                                ^\^       ^Sf.coruim'y  t^ 
miy-lit  not  only  liave 
been  proportional  t<) 
the  diameter  of  the 
primary  ring,  Imt,  in 
order    to  attain  the  '<* 
maximnm  effect,  the 
projection  of  the  sec- 
ondary coil   beyond 
the  plane  of  the  pri- 
mary might  also ha\e 
been    found   to  in- 
crease   in   like    pro- 
portion. 

This  led  ine  to  try  the  effect  of  a  conical  primary  coil  A  with 
the  Be(;ondary  B  at  its  apex,  as  shown  in  Fig.  9,  but  the  hear- 
ing distance  for  a  bullet  was  only  3.5  cm. 


iai 


lA 


Siiifiiilurl.v  enough    Mr.  •) . 
iii<l('|M'ii(|('ntly  iirrivtMl  at  ii  vt 

riff.  10. 


JVgtl 


II.  ('.  WiittM,  in    Bultinionf,  liiul 
IT  siinilur  I'oriu  ttt'  cuil,  iiixl  with 

till-     i  IIHt  IMMII  t'll  t 

rtli<»wii  ill  Fi;;.  H> 
lit!  Iiad  iilttiiiiHMl  tit 
i)iu>  tiiiut  a  hearing 
(iiHtaiice  ol  7.")  cm., 
(or  ''\  iiiciinH,' )  liiit 
In  (III  H»»iii('  caiiKO 
not  ascertained  he 
was  iiiialih!  siiiise- 
i|ii»MitJy  to  repro- 
duce the  effect. 

Tlie  tiiial    foiiii 
of  apparatus  adop- 
ted as  the  result  of 
^""■''  the    al)ove    experi- 

menttt  in  Khowii  in  V\^.  1 1.  With 
this  arranjfeineiit  ami  a  l»at- 
terv  of  six  hichroinate  elements 
freshly  set  up,  we  were  always 
sure  of  a  iiearinjjj  distance  of  at 
least  r»  cm.,  although  after  the 
battery  had  lieon  in  use  for  some 
time  the  hearing  distance  hurdly 
exceeded  4  cm. 

The  followin}?  are  the  diinen- 
iiions  of  the  coils  A  B  (Fig.  11) 
and  their  resistance : 


Coil,  A Exteruiil  iliiunoter 7     •'"'• 

luteriml  (liiiiueter 4.6  cm. 

Depth 2.4  cm. 

Wire  used,  No.  23,  (cotton  covered.)    ResiBtiince,  2  obms. 

Coil  li Exteruiil  iliiiuieter 2-"  cm. 

luteruul  diiuiieter **     vaxix. 

Depth »     '"»"• 

Wire  uned,  No.  3«,  (silk  covered.)     Kesiotiiiace,  75  ohms. 

'  See  Apjiendix,  uote  11. 


diinetj- 


17 

Tlu'  fii'T  of  tli<i  roil  H  projo('t«'«l  InnoiKl  tli«  faoo  of  coil  A 
4  iiiiii. 

Tlir  iialaiiciiig  «M)ilH  wi>n^  iiiiulo  hh  iicarh'  n*  poHHiiilc  tlin 
(hiplii-attif*  of  A  aii<l  H.  Tlie  n'sihtaiico  of  the  coil  of  tlu'  telu- 
pliuiie  eiiiplt»}'tHl  was  75  f»hin». 

fniiaence  of  liiittc.nj  I'lui'ei'. 

The  foUowiuff  iv\pi'riiii(!iitrt  were  iinuii!  with  thiH''a{»j)aratiirt 
(Fig.  11)  on  July  2(»th,  l«Hl,  to  tuHt  the  iiithmiiee  of  i)att('ry 
arratigemeiitH  upon  the  hearing  dihtaiice  of  a  leaden  hnllet. 

I.  SfrifM  iif  nperimentu  mth  a  bMiromatf  Ixittery  which  had  pmioiiHly  hti  n  in 

unefiir  afeip  minutfii. 


1  cell 

3  cpUh  in  HcriPH 

3  cells  in  MerieH 

4  cpIIh  in  HericM 

5  cells  in  HericH 

0  coIIh  in  HcricH 

(5  cellH  in  multiple  »rc 


Hearing  iliauiiice  of  liiidtn 
Inillei  at  obiervttl  by— 


6  ceils  in  two  serioa  of  H  eiicli . 


o 

o 

o 

o 

o 

o 

(>  oUh  in  three  Heries  of  2  each. 


o  w  o    I 
o  o  n    I 


II.  Series  of  exj}enm«nt»  with  a  Leclanchi  battery  of  twenty  eelln  which  had 
bfen  net  up  for  about  one  month,  ft  had  been  kept  nt/rmally  upon  open 
circuit,  and  had  only  been  occamonally  mted. 


20  cells  in  series 

20  colls  in  10  series  of  2  enoh. 
20  cells  in  .5  series  of  4  each... 
20  cells  in  2  series  of  10  each. 


Hearing  ilist.ince. 
3.3  cnj. 
3.6  ja. 
4.1  cm, 
3.0  cm. 


Althongh  the  battery  appeared  to  be  in  good  condition,  a 
close  inspection  showed  that  the  connections  were  dirty,  and 
that  one  of  the  zinc  wires  was  half  broken  throngh. 


■Hi 


18 


The  defective  cell  was  now  removed  from  tlie  cinmit,  and 
tlic  coinie(!tion8  of  all  the  other  cells  cleaned  and  tightene<i. 

III.   Th<;  folliming  experinwntH  were  then  made  \rith  tlw  Leclane/ii  eelln  united 

in  Kerien : 


No.  of  cells. 

Hearing  dis- 
ta.ice. 

nn. 

1 

2.7 

2 

2.H 

3 

3.0 

4 

3.3 

5 

3.3 

6 

3.5 

7 

3.(J 

8 

3.8 

S) 

4.0 

10 

3.8* 

No.  of  cells. 

Hearing  dis- 
tance. 

cm. 

11 

3.8* 

12 

4.2 

13 

4.2 

14 

4.2 

15 

4.3 

1(5 

4.2 

17 

42 

18 

4.2 

19 

4.2 

1 

These  results  are  gi-aphically  represented  in  Fig.  12. 

It  will  be  observed  that  the  hearing  distance  was  carried 
nearly  one-third  as  f.i.r  again  as  at  first,  simply  by  increasing 
the  number  of  c^ells  employed  withont  any  other  change  in  the 
arrangement.  It  will  also  Ite  noticed  that  the  apparatus  re- 
quires to  l»e  adjusted  to  complete  silence  in  order  to  ol)tain  the 
maximum  effect. 

As  a  general  result  of  all  our  e.\pei"imeiits  with  voltaic  bat- 
teries, we  find  that  it  vV  lulvisahle  to  uxe  a  battery  pofiseftrlng 
great  elertro-motive  force  and  slight  internal  resistance,  and  to 
connect  the  cells  in,  series. 

Krperinisnts  upon  Living  Siih}e<'ts. 

On  tlie  22(1  of  July  an  experiment  was  made  at  the  request 
of  Dr.  Bliss  upon  the  person  of  Lieut.  Simpson,  who  had  car- 
ried a  bullet  iu  his  body  for  many  years. 

When  the  exploring  instrument  (Fig.  11)  was  passed  over 
the  lieutenant's  back  a  sonorous  spot  was  found,  l)ut  the  indi- 
cations were  to^,-  feeble  to  be  implicitly  relied  upon.  Imagina- 
tion very  easily  conjv^res  up  a  feeble  sound  like  that  observed, 

*  Balunoe  not  qtiite  perfect. 


sssss 


rcnit,  and 
iitened. 
;'  nellx  united 


tig  dis- 


111. 

I.8» 

,.'2 
1.2 
L2 
1.3 
1.2 
12 
i.2 
i.2 


12. 

ivti»  carried 
'  increasing 
ange  in  the 
>paratns  re- 
)  ol)tain  the 

voltaic-  l)»'t- 

nice,  a/ul  to 


the  request 
^^ho  had  car- 
passed  over 
but  the  indi- 
i.  Imagina- 
lat  observed, 


,        ^ 

W 

>s 

■1 

N 

S 

s 

fe 

s? 

s 

:4 

'  ii 

tuKI'-^U 

HM^iOfl 

"  "~S 

R 

a 

1 

§ 

? 

- 

Vt^tfiy  J. 

TTMf  motm 

Vtf 

V 

« 

\ 

N 

\ 

<0 

<0 

' 

* 

\ 

•1 

\ 

«« 

M 

1 

*  >^  "5"     "» 

«9 


20 


M 


but  a  nuiiiiter  (.f  experiiiieuts  by  different  observers  seemed  to 
indicate  that  in  this  ease  there  was  an  external  cause  for  the 
g,,„n<l — probably  the  presence  of  a  very  deeply-seated  bullet. 
The  results  of  this  experiment  were  counnunicated  to  Dr.  Bliss 
in  a  letter  dated  July  '2;3d,  1881.' 

On  the  25th  of  July  Prof.  Rowland  visited  me  at  Washing- 
ton, and  suji;gested  the  use  of  a  condenser  in  the  primary  cir- 
cuit, r  had  previously  discussed  this  idea  witli  Mr.  Tainter, 
but,  not  having  a  (unidenser  at  hand,  we  had  been  unable  to  make 
any  experiment.  After  our  conversation  with  Prof.  Rowland, 
however,  we  wei  e  so  impresRed  i^y  the  importance  of  the  point 
that  we  obtained  a  condenser  next  morning,  and  found  it  to  pro- 
du(u;  not  only  a  different  (piality  of  sound  when  the  bullet  ap- 
proached the  coils,  but  also  to  increase  the  hearing  distance  of 
the  instrument  shown  in  Fig.  11  at  least  one  centimetre. 

On  the  evening  of  the  same  day  (July  2«>th)  our  apparatus 
was  carried  to  the  Executive  Mansion,  and  an  experiment  made 
upon  the  persoii  of  the  President.^ 

From  some  cause  then  unknown  a  balance  could  not  be  ol>- 
tained,  and  the  results  were  therefore  uncertain  and  indefinire. 
It  was  discovered  afterwards  that  a  mistake  had  l)een  made  in 
the  nuKle  of  (jonnectiug  the  condenser.  The  latter  should  have 
been  connected  at  E  F,  (Fig.  IJJ,)  whereas  it  was  placed  at  E 
(t,  tlms  iutlueucing  only  one,  instead  of  both,  of  the  primary 
coils. 

With  the  condenser  properly  ari-anged  experiments  were 
tried  on  July  29  and  80  on  three  soldiers  from  the  Soldiers' 
Home  who  had  been  wounded  during  the  civil  war,  namely, 
John  Teahan,  Asa  Head,  and  John  McGill. 

In  the  case  of  John  Teahan  no  results  were  ol)tained.  In 
the  case  of  Asa  Head,  who  had  a  buckshot  in  the  cheek,  loud 
and  well-marked  sounds  were  heard  in  the  telephone ;  and  in 
the  ci;se  of  John  McOill,  who  was  supposed  to  carry  a  bullet 
in  his  back,  no  resiilts  were  obtained. 

Further  efforts  were  then  prosecuted  for  the  improvement 
of  the  apparatus. 

'  See  Appoudix,  note  12. 
'  See  Appendix,  note  13. 


wm 


mi! 


22 

Further  K-rperhmnts  to  Improm  Apparatus. 

Our  attention  lm<l  hitherto  been  directed  ehietly  to  uiodifi- 
cationrt  of  tlie  exph)rin«,'  instrument.  We  now  investigated  the 
effect,  upon  tlie  hearinj,'  <listance,  of  the  coils  used  to  obtain  a 

hahince. 

Tlie  f.dlowing  experiments,  made  July  25>,  1881,  hear  upon 

the  point : 


Exp.  1.  (See  Fig.  14.)  Eesistance  of  primary  A  of  ex- 
ploring instrument,  2  ohms ;  resistance  of  primary  C  of  bal- 
ancing coils,  also  2  ohms ;  resistance  of  exploring  secondary  B, 
140  ohms ;  and  of  balancing  secondary  D,  120  ohms. 

Result :  Hearing  distance  of  bullet  from  explorer  A  B,  3.5 
cm.     Hearing  distance  from  balancing  coils  C  1),  also  3.5  cm. 

Exp.  2.  (See  Fig.  15.)  Same  exploring  coils  as  in  Exp.  1, 
but  balancing  coils  consisted  of  a  flat  primary,  E — resistance, 
5.30  ohms ;  and  flat  se(!ondary,  F— resistance,  83  ohms.  The 
adjustmen'  as  made  by  sliding  the  secondary  coil  upon  the 
primary  until  a  position  of  silence  was  obtained. 

Result :  Hearing  distance  from  explorer  A  B,  1.5  cm.  Hear- 
ing distance  from  E  F,  3  cm. 

As  a  general  result  of  our  experiments  we  found  that  evertj 


ipii 


lipii 


Hear- 


98 

increase  in  the  remHtunee  of  the  halamrny  cm'fs  (especially  the 
pniDarif)  reduced  tlie  Juiariiuj  distance  of  tlta  erplorinif  instru- 

rtgM 


m^M,  HUu  '>  becrtme  therefore  desirable  to  do  away  with  this 
source  of  resistance  as  much  as  possible. 

Return  to  Original  Foiin  of  Apparatus. 

This  led  us  back  to  the  original  form  of  apparatus  that 
had  lirst  occurred  to  me,  (see  Fig.  1,)  in  whicli  a  single 
pair  of  coils  was  employed.  A  few  other  experiments,  made 
July  29, 1881,  will  show  the  imrortance  of  the  point  attained. 

Exp.  3.  The  two  flat  coil*:,  E  F  used  in  experiment  2  were 
arranged  as  in  Fig.  16,  so  as  to  fo'-m  a  balance  by  themselves. 

Result :  Hearing  distance,  7  en.. 

In  all  these  experiments  the  battevy  ..^cd  consisted  of  four 
cells,  (Leclanishe.) 

ng.te. 


Exp.  4.  The  same  coils  used  in   Exp.  3  were  tried  again,  as 
shown  in  Fig.  16,  but  with  a  battery  of  eight  cells,  (Leclanche.) 


KM 


24 

Result;  Ilearinji;  clistiincie,  8.7   c.in,,  or   nearly  3^  inches — a 
result  quito  unprecedented  in  our  experiments. 

The  foUowinj^  are  tlie  dinioiisions  of  the  eoils  E  F: 

Coll,  !■; Extcriml  iliiuuot»'r lO      cm. 

Internal  iliaineter 2.5  cm. 

Depth 1      cm. 

Wire  used,  No.  *i'.\,  (silk-covereil.) 

Coil  F Rxternul  ilianutcr 10     cm. 

Internivl  (liiimetfr 2.5  cm. 

Diptli 1      cm. 

Wire  used.  No.  28,  (mlk-covered.) 


x      r 
Exi'.  5.  The  same  coils  E  F,  used  in  E.xps.  'i,  B,  and  4,  were 
tried  once  more  with  a  battery  of  six  large  bichromate  elements, 
and  with  a  condenser,  G,  in  the  primary  circuit  as  shown  in 

Fig.  17. 

Result :  Hearing  <listance  13  cm.,  or  more  than  5  niches. 

This  great  increase  in  hearing  distance  seemed  to  l)e  chiefly 
due  to  tL  condenser,  for  upon  disconnecting  it  the  hearing  dis- 
tance was  little  more  than  9  cm.,  but  further  experiments  proved 
that  other  causes  also  contributed  to  the  result. 

Exp.  6.  When  the  condenser  was  in  circuit  and  the  leaden 
bullet  close  to  the  coils  (arranged  as  in  Fig.  17)  the  sound  pro- 
duced by  the  telephone  was  a  musical  note  whose  pitch  was 
the  same  as  that  normally  produced  by  the  vibration  of  the 
reed  of  the  interrupter.  Mingled  with  this  tone  could  be  dis- 
tinguished a  number  of  feelder  tones  of  very  much  higher 
pitch.  Upon  withdrawing  the  bullet  gradually  fi  -ni  the  coils 
the  fundamental  sound  became  fainter,  and  one  of  the  high 
upper-partial  tones  gradually  acquired  pi-ominence  ;  and  at  a 
distance  of  about  8  or  9  cm.  the  fundamental  could  no  longer 
l)e  distinguished,  but  the  high  tone  persisted,  and  was  clearly 
audible  up  to  a  distance  of  13  cm.  The  effect  was  very  strik- 
iu".  and  when  the  bullet  was  moved  to  and  fro  j)arallel  to  the 


INHHItiMi 


imp 


iniiP 


96 


plane  of  the  coils  E  F  at  a  dititanco  of  about  10  cm.,  the  tel- 
ephone enntte<l  a  shrill  wiiistliniit  sound  each  time  the  sensitive 
area  (IF)  was  passed. 

It  was  noticed  that  other  metals,  such  as  iron,  brass,  and 
copper,  did  not  seem  to  reinforce  this  high  tone  to  any  great 
extent,  l)ut  brought  out  tlie  fundamental  at  every  distance  where 
an  effe<'t  was  produced. 

Exp.  7.  The  condenser  Ci  (Fig.  17;  was  removed  from  the 
circuit  and  the  leaden  bullet  held  al)out  4  or  5  cm,  from  the 
coils  E  F.  The  fundamental  tone  was  heard,  and  tlie  charac- 
teristic upper-partial  (tould  also  be  distingviished,  l)ut  it  was 
only  faintly  audil)le.  Upon  now  suddenly  replacing  the  (v»n- 
denser  tlie  high  upper-partial  toTie  was  instantly  reinforced  as 
if  by  a  resonator. 

Exp.  8.  The  rheotome  employed  to  interrupt  the  primary 
circuit  (which  had  l)cen  pla<!ed  in  a  distant  room)  'vas  found 
to  be  viltrating  badly.  The  reed  I  of  the  instruiiient  (see  also 
Fig.  5)  was  rattling  against  its  contact  pieces,  thus  producing 
an  impure  sound,  and  1  couhl  distinguish  amongst  the  upper- 
partials  the  tone  that  had  been  reinforced  by  the  condenser. 
Upon  screwing  up  the  contact  pieces  so  as  to  improve  the  vi- 
bration I  could  no  longer  distinguish  the  particular  upper-par- 
tial referred  to,  and  upon  returning  to  the  room  in  which  tiie 
coils  E  F  (Fig.  17)  were  placed  I  could  no  longer  detect  the 
effects  noted  above  in  Exps.  6  and  7,  and  the  hearing  distance 
did  not  exceed  t'  .mi. 

The  jnoaliar  effects  obtained  with  the  arranijemeat  shown  in 
Fig.  17  thus  seemed  to  depend  (1)  upon  a  particular  kind  of 
vibration  of  the  reed  o^  the  interrupter,  producing  a  certain  high 
upper-partial  or  overtone,  (2)  upon  the  use  of  a  condenser  act- 
ing as  a  sort  of  electrical  resonator  for  this  tone,  and  (3)  upon 
the  use  of  the  metal  lead. 

Mr.  Marean,  of  Washington,  kindly  lent  me  a  number  of 
condensers  used  by  the  Western  Union  Telegraph  Co.,  and  we 
found,  upon  connecting  them  with  the  coils  E  F,  as  shown  in 
Fig.  17,  and,  holding  a  leaden  bullet  near  the  coils,  that  each  con- 
denser reinforced  a  high  upper-partial  of  different  pitch.  We 
arranged  tlie  condensers  so  that  they  could  be  successively  in- 


mmmmmimitiimmm 


mmm 


M 


.1 


tro(hu!e(l  into  the  eircuit  with  great  rapidity.  Tlie  effect  was 
very  curiouB,  and  sounded  somewhat  Hl<e  a  Scotcih  air  played 
npon  the  hag-pipeH.  Tlie  U)W  hum  of  tlie  fundamental  couhl 
he  heard  continuously,  like  tiie  drone  of  the  Itag-pipe,  while 
the  higher  tone  cluvnged  ita  pitch  with  each  change  of  con- 
deuHer. 

The  pitcli  of  till'  hUjh  ione.  rn'uifori-eil  tti'i'ined  to  (hpend 
upim  the  devtro-Htatk  capacitij  of  the  coiit/eim'r  employed,  but 
the  exact  relation  between  the  two  has*  not  l>een  aHcertained. 
In  experiments  5,  6,  7,  8,  and  the  suhsequent  experiments  de- 
scribed above,  the  battery  employed  (ionsisted  of  six  pairs  of 
(!arl»on  and  zinc,  plates  of  large  area  placed  in  a  solution  of  bi- 
chromate of  potash  containing  sulphuri*^  acdd. 

The  effects  noted  above  were  not  produced  satisfactorily 
when  the  battery  was  much  run  down,  nor  were  they  oi)tained 
with  a  Ledanche  battery  which  had  l)een  set  up  for  soine  time, 
but  which  appeared  to  be  in  good  condition. 

It  Itt  eiudently  neremi/'y  in  order  to  produee  this  eharactcr- 
idic  high  tone  to  use  a  buttery  possesMiu/  coiisideraUe  electro- 
motive force  and  slight  internal  resistance. 

Our  experiments  had  i-eached  this  stage  wlien,  on  Saturday, 
the  30th  of  July,  1881,  I  was  reijuested  to  make  another  trial 
upon  the  person  of  the  President  at  the  evening  dressing  of  the 

wound. 

At  this  time,  however,  we  had  no  exploring  instruments 
completed  excepting  one  or  two  like  that  shown  in  Fig.  11 ; 
for  it  will  be  understood  that  the  pi-omising  results  noted  above 
had  been  obtained  from  coils  that  were  simply  placed  upon  a 
table  and  adjusted  by  hand. 

We  immediately  proceeded  to  the  Executive  Mansion  with 
the  apparatus  shown  in  Fig.  13,  prepared  to  make  a  trial,  if  it 
was  deemed  advisable ;  but  upon  learning  of  the  results  of  our 
later  experiments  the  surgeons  resolved  to  postpone  any  further 
trial  imtil  we  could  arrange  the  coils  (Fig.  17)  in  a  portable 

form. 

By  forced  exertions  the  c^ils  were  arranged  that  same  night 
in  a  wooden  case,  as  shown  in  Fig.  18.  This  ease  consisted  es- 
sentially of  two  oblong  blocks  A  B.     A  shallow  circular  recess 


'•'X^: 


it'jaa»iiaSi»w^ji»>!wuWM 


rf 


ts 

waH  turned  out  in  each  l)lo(^k  for  the  re(!eption  of  one  of  the 
coHh,  and  flii^  two  Mockrt  were  held  together  hy  four  \)\m  of 
elH.iiite,  (',!),  K,  F,  wliich  paHwed  up  through  Aotn  in  the  upper 
hhick  and  were  seeured  hy  eliouite  tlunnl)-M'rewK. 

When  the  iuHtrunient  wan  f(>ni|)hited  I  found  to  my  great 
diHtrehH  that  a  hahince  eouhi  not  he  ohtuined  l)y  an}  adjnst- 
nieuf  of  the  apparatUH.  Tiiere  was  a  position  of  niininiuni 
sound,  an<l  the  te.ej)hone  resi)onded  to  a  hullet  presented  to  the 
(tentral  part' (t  of  tlie  instj-uuient ;  hut  tlie  hearing  distance  did 
notex(^eed  ;}  or  4  cm.,  whereas  we  had  (>htained  with  tlie  same 
coils  hefore  the  ecuistruetion  «)f  the  wooden  case  a  perfect  l»al- 
aiice  and  a  hearing  distance  of  l'^  em. 

After  numerous  unsuccessful  experiments  had  been  made  to 
ascertain  the  cause  of  the  ditticult}'  it  occurred  to  Hie  that  if 
two  adjoining  convolutions  in  (me  of  tlie  (M>ils,  made  (^mtact 
at  any  point,  a  circuit  of  low  resistance  would  he  formed,  (a 
single  ring  of  wire,  in  fa(!t,)  in  which  the  induced  currents 
might  circulate  without  reaching  the  telephone  connected  with 
the  apparatus.  I  had  previously  measured  the  resistancre  of  the 
coils  without  discovering  any  defect,  hut  when  I  considered  the 
large  nund)er  of  convolutions  in  each  coil  it  seemed  possihlc 
that  a  defect  of  this  kind  nnght  exist  which  couhl  not  he  dis- 
covered hy  a  Wheatstone  Bridge,  excepting  hy  very  delicate 
and  accurate  oliservations.  To  test  whether  a  short-circuited 
convolution  would  produce  effects  analagous  to  those  oi)served, 
a  piece  of  copper  wire  was  hent  into  an  amndar  form  and  the 
ends  connected  together.  On  hringing  this  metallic  ring  near 
a  pail  of  (mils,  (A,  B,  Fig.  19,)  properly  adjusted  to  silence,  the 
halanc^e  was  loudly  disturhed.  The  copper  ring  (C)  was  held 
as  shown  in  Fig.  19,  and  the  halance  could  not  then  l)e  re- 
stored hy  any  adjustment  of  the  coik.  A  position  of  miuimum 
sound  was  all  that  couhl  he  ohtained,  and  the  hearing  distance 
was  enormously  reduced.  This  was  prima  facie  eviden<;e  of  the 
nature  of  the  <lefect. 

The  coils  (F'ig.  18)  were  then  removed  from  their  case,  hut 
a  cursory  examination  revealed  no  defect.  Upon  trial,  how- 
ever, (heing  arranged,  as  formerly,  in  Fig.  17,)  a  halance  could 
not  he  ohtained,  and  the  hearing  distance  was  only  ahout  4 


imM 


Ml 


IV 


29 

om.     Tlio  (IcfiH^t  WBH  thiiH  (Infinitely  located  in  tlio  eoiln  thein- 
Bolvort. 


Upon  c.loKe  exaininiition  it  was  notitred  that  the  outrtide  vmw- 
vohitioiirt  of  tiie  primary  (toil  were  slightly  frayed  at  one  part, 
hut  it  appeared  hardly  possible  that  ho  great  a  defect  could  he 
due  to  bo  apparently  slight  a  (tause.  However,  to  test  the  mat- 
ter, I  removed  the  outside  layer  of  wires  and  then  tested  the 
coils  again. 

Result :  The  (lefe(tt  had  vanished — a  perfect  balance  M'as  ob- 
tained, and  the  hearing  distance  was  again  13  cm.* 

The  (toils  were  then  rephuted  in  their  (tase  and  the  completed 
instrument  tested.     The  lower  wooden  block  B  (Fig.  18)  was 

'  These  oxperiiiicuts  hiive  revonled  tho  cause  of  the  extreme  difllculty  ulwtiys 
experienced  iu  obtiiiuiiig  u  perfect  biilunce  with  coils  of  line  wire.  I  have 
recently  used  iiu  Induction  Biilunce  to  test  the  condition  of  the  tielices  tliiit 
were  employed  in  these  researches,  and  liave  discovered  that  iu  a  large  per- 
centage of  cases  tlie  insulation  was  (h^fectivo.  It  is  possible  that  some  of  the 
results  descriV)ed  in  this  paper  (especially  of  the  earlier  experiments)  may 
have  been  vitiated  by  errors  due  to  defects  in  the  coils  that  were  not  sus- 
pected at  the  time.  A  defect  of  insulation  that  is  quite  immaterial  for  ordi- 
nary purposes  maybe  absolutely  fatal  to  the  success  of  an  Induction  Balance. 
Indeed,  so  much  care  is  required  in  this  resjjoct  that  it  is  extremely  difficult 
to  obtain  coils  that  are  perfectly  suitable  for  an  apparatus  intended  to  search 


ir 


iirtiiiiiiliiw^ 


rr" 


V-  ."V 


80 

H«ljiirtt««l  l>y  luuid  HH  iwnr\y  iik  poH^iMi-  to  tln'ptwitiiin  of  hIUmu'c, 
1111(1  tlicii  the  tliniiil.-8<-n'\vs  (',  I),  K,  F  w»t."  ti^'litciifd. 

Tlu!  Iiiiliinct'  iKiw  ol.tiiiiuHl  WHS  not  <|iiitt»  portWt,  lnit  l>,y 
htrikiii"  tin-  lowi'i-  lilock  H  a  f«'W  Hiiiurt  IdowH  with  a  wo(mIi)H 
iiiallft  wv  wvw  al»Io  to  vvAwv  tim  arruiij;(Miiont  to  (•oiii|)lotn 
Hiloiict'. 

Tlu^  iiiKtrmiU'iit  wan  thou  in  siicli  a  wMihitivo  coiKiitioii  tliat 
it  could  Hcarcd.v  Ix-  iuovcmI  without  aft'cctiii^'  t\\v  l)alan<'«.  Hpoii 
gently  swayiiiK  it  hackwardrt  an<l  forwanln  apulnation  of  Hound 
was  heard  at  every  nwing. 

Wiien  the  motion  whh  carefully  made,  ho  that  it  was  always 
in  the  nanu'  plane,  no  ])idsationH  were  oiiserred.  They  only 
occurred  when  the  indinati f  tln^  coils  waw  changed. 

ThiH  defect  waH  found  to  he  due  to  the  l>ulging  of  the  thin 
portion  (4  of  the  wooden  cane  (Fig.  18)  under  the  weight  of 
the  enclosed  coil,  and  tlut  simple  pressm-e  of  a  finger  on  thia 
portion  of  the  case  distm-l)ed  the  balance.  The  movement  of 
the  l(»wer  «'oil  when  the  instrument  was  swayed  ahout  nnist 
have  heeii  ineoTiceivahly  small,  hut  on  account  of  the  extreme 
sensitiveness  of  the  arrang<iment  it  produced  a  per(;eptii)le 
effect  upon  the  hahmce. 

The  pidsating  sound  did  not  seeni  t(.  interfere  with  the  de- 
tection of  a  bullet  held  in  the  clenched  hand,  nor  did  it  seem 
to  affect  the  hearing  distan(^e.     1  therefore  despatched  u  mes- 

out  IV  bullet  iuibediUnl  in  the  body.  I  now  uiiike  it  a  rule  to  test  every  helix 
UHed  in  Induction  HnliincP  i-xiierinieuts  by  bringing  it  up  to  »  system  of  bal- 
anced coils  like  thivt  hIiowu  in  Fig.  17. 

1.  If  the  helix  is  perfect  the  balance  if  not  disturbed  until  the  terminals  of 
the  coil  are  connected. 

'2.  If  there  is  a  break  in  any  ^  the  convolutions  the  balance  is  not  disturbed, 
even  when  the  terj..uials  are  f. ui  lected. 

H.  If  a  convolution  is  shi.s-).--  ircuited  the  balance  is  disturbed,  even  though 
the  tenninals  are  not  connect  jd,  and  the  sound  produced  is  the  fundamental 
of  the  rheotonie  employed  to  interrupt  the  primary  circuit. 

4.  If  the  insulation  is  defective  the  balance  is  disturbed,  although  the  ter- 
minals are  not  comiected,  and  a  peculiar  spluttering  eflfect  is  noticed  like  that 
l)roducod  by  a  series  of  sparks. 

I  propose  to  apply  this  method  practically  as  a  means  of  testing  the  condi- 
tion of  the  helices  used  in  the  ccmstruction  of  Induction  Coils  and  those  em- 
ployed in  the  manufacture  of  telephones. 


M 


HOijjor  tn  till'  Kxrciitive  MiitiHioii,  CSuiidiiv  luoniirif?,  .Iiilv  Hint,) 
with  a  iioto  for  Dr.  HUhh,'  to  U'\  liiiii  kiinw  tiiiit  tlio  iiiHtriiiiiciit 
wiw  in  a  (fuixlitioii  ti»  lie  iiHed,  Hlioiild  iiiiy  iiet^oHrtity  liriwi  for 
an  inun('<liut((  fxiMn-iininit.  At  tlio  HHin«  time  I  inf<>nne<i  him 
that  till!  ajiparatiirt  iti  its  prewMit  form  wan  very  (M-ildely  fon- 
Htr\ict»'(l,  and  that  I  hoped  to  improve  it  very  jjjreatly  in  the 
eourwe  of  a  tew  dayw.  Oti  Siidday  afternoon  (.Inly  .'Urtt)  we 
Hent  to  tne  Soldiers'  Home  for  John  Mcdill,  npctn  whom  wo 
had  experimented  the  previoiiH  day  withont  rennltfl,  (using  the 
apparatus  shown  in  Fig  11.) 

Upon  trying  the  nesv  instrnment  (Fig.  1^)  we  had  no  ditti- 
<Mdty  in  finding  a  sonorous  spot  in  his  haek,  at  the  place  where 
the  hullet  was  always  supposed  t<j  lie. 

This  result  wjis  at  o\we  eonumuiic-ated  t<t  Dr.  Bliss,'  and  in 
repl}'  we  were  re(|uested  to  make  the  experiment  upon  the 
person  of  the  President  next  morning. 

On  Monday  morning  (August  Ist,  1881)  wo  aceordingly  re- 
moved our  aj)paratus  to  the  Kxoeutive  Mansion. 

77te  Late  I'reshlen'  (rarjield. 

During  the  former  experiment  (-ruly  26)  a  sudden  sono- 
rous effect  had  heen  oliservcd  upon  passing  a  point  near  the 
spot  where  the  surgeons  suspected  tiie  i)ullet  to  he  lodged, 
hut  1  had  i>oen  uiialde  to  verify  this  hy  a  second  ohserva- 
ti(m,  altlKMigh  the  exphtring  instriunent  (A  B,  Fig.  13)  was 
repeatedly  ])assed  over  the  same  place.  The  sound  had  heen 
so  loud  and  well  marked  that  T  helieved  at  the  time  it  nmst 
have  heen  (^ansed  hy  a  Budden  irregularity  in  the  viliration 
of  the  reed  of  the  rheotome  used  to  interrupt  the  primarj- 
eircuit,  for  the  arrangement  (as  explained  above,  p.  20)  was 
not  perfectly  balanced,  and  any  irregularity  of  this  kind 
would,  under  these  circumstances,  have  aflPccted  the  tele- 
phone. At  the  same  time  the  coincidence  was  remarkable 
that  the  exploring  instrument  should  have  been  at  that  very 
time  so  near  the  suspected  seat  of  the  ball,  and  this  led  to 
the  thought  that  perhaps  after  all   the  l)ullet  had  been   the 

1  8ee  Appendix,  note  15. 
'  See  Appendix,  note  14. 


■Ml 


Hi 


iM 


^mi 


caiiHo  of  tlu!  soniul.  I  felt  (ionfidont  that  the  new  instrii- 
iiieiit  (Fig.  18)  WMMihl  ut  once  <lcci<le  the  (jiie.stioii,  for  the  ex- 
treme hearitig  (iis;;iii<-e  of  the  former  apparatus  (Fig.  13)  was 
only  ♦)  ctn.,  and  tlie  apparatus  siiown  in  F'ig,  18  was  so  supe- 
rior in  this  respect  that  if  the  sound  had  really  been  due  to  the 
hullet  we  siiould  obtain  with  the  new  instrument  distin(!t  and 
well-marked  effects.  When  the  new  explorer  (Fig.  18)  was 
passed  over  the  suspected  spot  notiiing  was  heard  excepting  a 
slight  pulsating  sound  as  the  instrument  was  moved  to  and  fro. 
This  was  evidence  to  me  that  the  former  sound  had  been  of  ac- 
cidental origin,  wiiether  the  bullet  was  there  or  not.  Witli  the 
view  of  eliminatiiig  any  error  of  oltservation  caused  by  the 
pulsations  'lue  simply  to  the  movement  of  the  instrument,  I 
lifted  the  latter  (without  changing  the  inclination  of  the  coils) 
to  a  height  of  about  50  centimetres  above  the  body  of  the  Pres- 
ident, and  moved  it  to  and  fro  in  as  nearly  as  possible  the  same 
way  I  had  done  at  the  lower  elevat:o;i. 

I  presumed  that  if  the  pulsations  heard  were  (itie  simply  to 
the  movement  of  the  instriiment,  they  should  occur  with  equal 
strength  at  the  two  elevations ;  hut  if  any  portion  of  the  sonor- 
ous effect  was  due  to  the  inHueture  of  the  bullet,  the  pulsations 
at  the  two  (ilevacions  would  l»e  different  in  intensity.  I  was 
struck  by  the  fact  that,  although  the  sonorous  pulsations  were 
very  feeble,  they  were  sensibly  louder  wlien  the  instrument 
Avas  dose  to  the  surface  of  the  bodv  than  when  it  was  raised. 
Contimiing  the  exploration,  I  found  a  considerable  area  over 
which  simihu"  effects  were  noticed,  but  upon  carrying  the  in- 
strument towards  the  back  of  the  President,  the  diflfereiuje  be- 
tween the  pidsations  produ(!ed  at  the  two  elevations  grew  less 
and  less,  and  tinally  coidd  not  be  distinguished. 

The  diffeniuce  in  tlie  loudness  of  the  sound  at  the  two  ele- 
vations was  so  slight  that  it  probably  would  not  have  been  no- 
ticed by  an  esir  unaccustomed  to  listen  to  feeble  effects,  and  I 
feared  that  the  general  expectation  that  the  bullet  would  be 
found  in  that  part  of  tlie  body  might  iiave  led  me  to  imagine 
a  difference  that  did  not  exist.  For  the  purpose  of  eliminating 
as  far  as  possible  any  personal  error,  I  recpiested  Mr.  Sumner 
Tainter  (wh  >  was  the  only  other  person  present  whose  ear  had 
been  sufficiently  Iruiaed  to   l)e  reliable  in  such  an  emergency) 


rrr^^  ■  •--^5■JT^T35-•riT?5■•SS!t^BRWMK■•?^SKKSr■•:■■■ 


nmmffMtiis^iisiiimes^^iais^xsf 


mm 


wa 


33 


new  iuwtni- 
for  tlie  ex- 

'ig.   13)  W!18 

van  so  supe- 
II  due  to  the 
llstiii(!t  and 
''ig.  18)  was 
axcepting  a 
I  to  and  fro. 
been  of  ac- 
Witli  tlie 
ised  by  the 
irttninient,  I 
)f  the  coils) 
of  the  Pres- 
ble  the  same 

io  simply  to 
I-  with  equal 
»f  the  sonor- 
le  pulsations 
sity.  I  was 
sations  were 
instrument 
was  raised, 
le  area  over 
rying  the  in- 
ift"eren(!e  be- 
16  grew  less 

the  two  ele- 
ive  been  no- 
ffec^ts,  and  I 
et  would  be 
)  to  imagine 

eliminating 
Mr.  Sumner 
hose  ear  had 

emergentiy) 


to  repeat  tiie  experiments  and  let  ine  know  the  result.  Upon 
our  return  to  my  laboratory  we  compared  notes,  and  I  found 
that  his  observations  tallied  with  mine.  lie  declared  he  could 
not  obtain  a  distinctly  localized  effect,  l»ut  stated  that  he  had 
observed  a  reinforcement  of  the  pr.lsation  over  an  area  of  a*^  least 
two  inches  in  the  neigiiborliood  of  the  spot  to  which  his  atten- 
tion had  primarily  lieen  directed,  and  that  he  wiS  (Minvinced 
that  the  bullet  was  within  that  area. 

It  appeared  reasonaldy  cairtain  that  the  area  t>f  feiible  sound 
was  due  to  some  external  cause,  and  was  not  simply  a'  effect 
of  expi'c^tancy.  In  tlie  'absence  of  any  other  iipp:\"eiit  (^aiise 
for  the  phenomenon  I  was  forced  to  agree  in  the  cionclusion 
tiuit  it  was  due  to  the'preseiKie  of  the  bulhit,  and  I  so  stated  in 
my  report  to  the  Hurge(ms. '  I  was  by  no  means  satistied^ 
however,  with  the  results  obtained,  for  no  such  effects  had  been 
observed  liefore  i'l  our  experiments  with  ludletx.  I  tried  to 
reproduce  the  effects  by  moving  the  instrument  (Fig.  18)  at 
different  distances  over  a  bullet,  I)ut  in  every  case  where  an 
effect  was  produced  the  soinid  was  (juite  sharply  localized.  I 
thought  that  perhaps  the  Ixidy  of  the  patient  might  have  af- 
fected the  result,  and  so  experimented  upon  a  ])ullet  buried  in  a 
piece  of  meat,  but  no  difference  of  effect  was  noted.  This  led 
me  to  fear  that  the  extensive  area  of  feeble  sound  might  have 
Iteen  due  to  some  extensive  area  of  metal  that  was  unsuspected 
at  the  time,  and  I  proceeded  to  the  Executive  Mansion  next 
morning  (August  2)  to  ascertain  from  the  surgeons  whether 
they  were  perfectly  sure  that  all  metal  had  been  removed  from 
the  neighborhood  of  the  oed.  It  was  then  recollected  that 
underneath  the  horse-haii  mattress  on  whicth  the  President  lay 
was  anotiier  mattress  composed  of  steel  wires. 

Upon  obtaining  a  duplicate,  the  mattress  was  found  to  con- 
sist of  a  sort  of  net  of  woven  steel  wires,  witli  large  meshes. 
The  extent  of  the  sonorous  area  luiving  l)een  so  small,  as  com- 
pared with  the  area  of  the  bed,  it  seemed  reasonable  to  con- 
dude  that  the  steel  mattress  had  produced  no  detrimental  effect.^ 

•  See  Appendix,  note  l(i. 

"  The  deivtb  of  President  Giirfield  imd  the  subsecpient  poMt-tnorUm  exiini- 
iuatiou,  however,  proved  that  the  Imllet  was  ut  too  greiit  a  distance  from  the 
surface  to  have  affected  our  appiiratus. 


84 

I  WHS  unable  to  continue  exporinientrt  with  the  steel  mattress,  as 
just  at  this  time  I  was  obliged  to  leave  Wasliington  on  account 
of  illness  in  my  family.  A.ltliough  I  was  unable  for  a  long 
time  afterwards  to  carry  on  personally  lndu(!tion  Balaiuje  ex- 
periments, the  investigations  were  ably  (!ontinue*l  under  my 
direction  l)y  Mr.  Tliomas  Gleason,  in  tho  establishment  of  Mr. 
Charles  Williams,  Jr.,  in  Boston. 

Kj^perimentit  Conthvue,d  in  Boston. 

Mr.  Tainter  forwarded  from  Washington  drawings  of  an 
improved  apparatus  he  had  designed  to  remedy  the  defects  of 
the  instrument  shown  in  Fig.  18,  in  which  the  ease,  adjusting 
screws,  itc,  were  all  to  Ite  composed  of  ebf»nite. 

Mr.  Gloason  constructed  for  me  a  number  of  such  ebonite  <-. 
struments  differing  slightly  from  one  another  in  detail,  and  tiic 
apparatus  shown  in  Fig.  20  comltined  the  different  points  that 
had  l)een  approved. 

The  two  (!oils  A  B  were  ectcentrically  arranged  in  two  cir- 
cular disks  of  el)onite,  C  D,  and  tiie  adjustment  was  t»btained 
by  means  of  an  ebonite  key  O,  like  the  key  used  for  tuning 
pianos,  whi(!h  turned  a  cam  M  pivoted  in  the  upper  disk  and 
working  in  a  slot  K  in  the  lower  di^.k. 

ill  order  to  prevent  any  movement  of  the  coils,  excepting 
that  produced  Ity  tlie  adjusting-key  O,  each  coil  was  placed  in 
a  recess  turned  out  in  its  ebonite  disk,  tlie friges  of  which  were 
bevelled  as  shown  at  R.  Paratline  was  then  poured  in  so  jis 
to  fill  up  eacdi  recess.  But  this  alone  di<i  not  prevent  a 
sl'ght  pulsation  of  sound  when  the  instrument  was  swayed  from 
side  to  side,  and  a  very  slight  pressure  ut  the  finger  on  the  thin 
portion  of  the  ebonite  plate  under  tlie  coil  B  was  sufKcient  to 
destroy  the  balance. 

This  was  remedied  by  strengthening  this  portion  l)y  means 
of  a  rod  of  el)oiiite,  which  passed  up  through  the  centre  of 
the  (!oil  and  through  a  slot  F,  in  the  upper  ebonite  plate,  and 
was  clamped  firmly  after  tlie  adjustment  of  the  instrument 
by  an  elxmite  thunil>-scrow  II.  Tin's,  however,  increased  the 
difficMilties  of  adjustment.  When  the  c<tils  were  adjusted  to 
silence,  tlien  the  tiglitening  of   the  tliuml>-scrow    II  disturbed 


wmmmmmm 


3S 


'-liiliiiiiiHMiiiiil^^ 


86 

the  l)aliuuie  ;  and  if  tlio  1 1  in  ml  (-screw  H  was  tightened  firwt, 
then  the  adjuistnient  r.onU  only  he  made  l)y  a  series  of  jerks, 
4m  Hwount  of  friction.  In  practice  we  found  it  l)est  to  adjust 
the  instrument  tiiinost  fit KHi'/iif,  tmd  then  the  tightening  of  the 
thumli-screw  II  completed  the  halance. 

This  was  the  fomi  of  apparatus  ..I  whicli  we  had  arrived  at 
the  time  of  the  death  of  President  (rartield. 

The  difficulty  of  adjusting  the  c<(ils  led  nie  ultimately  to  the 
idea  of  the  apparatus  shown  in  Figs.  21,  22,  23,  24,  which  is 
the  most  practical  form  of  the  instrument  yet  devised. 


Fi^.ai. 


The  two  exph)'ing 
coils  A  \\  (Fig.  21)  are 
arranged  as  shown,  in  a 
recess  turned  out  in  a 
single  block  of  wood  0. 
The  coils  are  tempo- 
rarily connected  with  a 
telephone,  battery  and 
rheotome  in  the  manner 
I  shown  in  Fig.  1,  so  that 
they  may  be  adjusted  by 
hand  to  form  a  balance. 
When  they  have  been 
arranged  in  their  posi- 
ti  Ml  of  silence  the  hol- 
low in  theldock  of  wood 
C  (Fig.  21)  is  filled  with 
melted  paraffine.  Upon  (tooling,  the  two  coils  are  found  im- 
movably fixed  in  one  solid  cake  of  paraffine. 

As  a  matter  of  practice  it  is  found  impossible  to  fix  the  c(»il8 
in  this  way  exactly  in  tlieir  position  of  silence  ;  but  by  means 
of  two  other  very  small  coils,  D  E,  (Fig.  22,)  of  insignificant 
resistance,  forming  a  sort  of  fine  adjustment  external  to  the 
explorer,  a  perfect  l)alance  is  easily  obtained.  In  this  instru- 
ment the  swaying  of  the  coils  A  B  prodnces  no  offiPict  upon 
the  balance. 

The  completed  arrangement  is  shown  in  plan  in  Fig.  22, 
and  the  explorer  and  balancing  coils  are  shown  separately  in 
perspective  iuFigs.  23  and  24. 


'W5SS 


/'iw^wtsw-tiraiawi 


-<'r'?i'isss:    lism 


I 


I 


.; 


»7 


MHiiiiillil 


MiM 


iiiilMlMMiiii 


158 


Fiff.ZS. 


Mi 


On  account  of  the  Kniiill  nize  and  rtli^ht  rcHistance  of  the  bal- 
anciiif,'  cotlrt  we  were  enabled  to  make  the  adjustable  parts  of 
the  balancer  of  metal  without  practical  interference  with  the 
sensitivenerts  of  tlie  exploring  instvunient,  and  this  gave  us  the 
power  of  making  very  delicate  adjustments  of  the  l)alancing 

We  found  it  advisable,  however, 
to  avoid  placing  metal  over  the 
sensitive  area  of  the  coils  as  had 
been  done  in  the  instrument  shown 
in  Fig.  '24. 

In  the  balancing  apparatus 
Hhown  in  Fig.  25,  (which  is  the 
most  perfect  one  yet  <!onstructed,) 
tlie  lever  to  which  the  upper  coil 
is  attached  is  made  of  hard 
rubber. 
In  Fig.  26  is  shown  the  most  convenient  form  t»f  case  yet 

devised  for  holding  the  exploring  coils. 

By  invitati(»n  of  Dr.  Frank 
^^^^  -^^^fc.    Hamilton    experiments    were 

made  at  his  office  in  New 
York  October  7, 1881,  the  \\\- 
struments  used  beuig  those 
shown  in  Figs.  22,  23,  24. 
As  tliis  was  the  first  suc- 
cessfid  application  of  the  Induction  Balance  to  the  discovery 
of  the  situation  of  a  ball  in  the  l)ody  the  position  of  which 
was  previously  unknown,  I  may  be  pardoned  for  entering  some- 
what into  detail. 

I  shall  quote  from  the  Mediml   (iazetU>,^  of    New  York,  an 
account  of  the  experiments  written  by  one  of  the  witnesses : 

"  Th£,  First  Suecessfid  Application. 

"  On  Friday,  Oct.  7,  l)y   invitation,  several  medical  gentle- 
"  men,^  inclvidiujr  the  writer,  met  Prof.  Bell  at  the  house  of 

1  See  Mediml  GmetU,  Oct.  15,  1881,  pp.  347-349. 

3  ' '  The  f  ollowdiig  are  tLe  names  of  the  medical  gentlemen  who  were  present, 
"  each  one  of  whom  verilie  1  perHonally  the  reHnlts  ami  declared  his  entire 


"'i 


1 


88 

"  Dr.  Fmnk  II.  Ilaniilto!!,  in  tliiw  city,  for  the  purpose  i»f  wit- 
"  iiessiiig  the  praflical  iippli.'dtion  of  his  improved  inetniiiient. 

"  Tiie  tii'rtt  person  Hiilijoctcd  to  experiiueiit  was  General 
"  Calvin  E.  Pratt,  jiulfjjo  of  tlie  supreme  court  of  the  State  of 
"  New  York,  and  who  is  now  a  resident  (tf  Brooklyn.  Gone- 
"  ral  Pratt,  at  the  hattle  of  Gaines' Mills,  June,' 18()2,  this 
'  heing  the  second  day  of  the  famous  seven  days'  retreat  across 
"  the  peninsula,  received  a  l)all  in  his  left  cheek,  vvhidi  peue- 
"  trated  through  the  luires  and  was  lodged  in  tiie  right  antrum. 
"  Its  presence  at  this  time  was  recognized  hy  his  surgictal  at- 
"  tendant,  Dr.  Damainville,  and  its  exact  position  has  lieen 
"  known  from  that  day  until  this,  it  having  given  rise  at  times 
"  to  nmch  pain  and  suffering. 

"  General  Pratt  has  been  seen  hy  Dr.  Hamilton  and  Dr. 
"  Damainville  occasionally  from  that  time  forward,  and  they 
"  have  from  time  to  time  urged  upon  him  the  necessity  of  its 
"  removal.  General  Pratt,  however,  was  anxious  to  ktiow 
"  whether  Prof.  Bell's  instrument  would  indicate  its  presence 
"  at  the  same  point  as  declared  hy  his  surgeons. 

'"  The  results  of  the  experiment  were  conclusive  and  entirely 
"  satisfactory  to  General  Pratt,  the  response  heing  heard  dis- 
"  tinctly,  hut  rather  feehly,  hy  every  person  present  in  the 
"  room.  The  feei)lene8s  of  the  pesponse  was  supposed  to  he 
"  due  to  the  fac^t  that,  owing  to  its  situation  and  the  peculiar 
"  form  of  the  instrument  containing  the  induction  coils,  it  was 
"  impossihle  to  l)ring  the  centre  of  its  surfatte  very  near  the 
"  site  of  the  hall,  the  hall  heing  situated  very  near  the  depres- 
"  sion  at  tlie  ala  of  the  nose." 

"  Tlie  next  patient  was  Col.  13.  F.  Clayton,  who  received  a 
*'  wound  at  the  hattle  of  Cedar  Mountain,  Virginia,  Aug.  9, 
"  1862. 

"  Tiie  missile  was  supposed  to  he  an  P^nlield  rifle  hall,  and 
"  tiie  wound  was  supposed  to  he  mortal  isy  tlie  medical  director 
"  of  General  Banks'  staff  and  his  assistants.  The  l)all  passed 
"  through  the  sternal  end  of  tli^  left  clavicle,  and  was  supposed 
"  to  have  lodged  in  the  muscles  under  the  superior  angle  of  the 
"  corresponding  scapula.  Tlie  injury  was  followed  hy  complete 
"  paralysis  of  the  left  arm,  continuing  for  a  period  of  six  months  ; 
"  and  his  arm  has  never  yet  been  <!ompletely  restored  to  its  noi-- 
"  nial  condition.  He  suffers  a  great  portion  of  his  time  from 
"  pains  in  the  arm,  slujulder,  and  portions  of  the  back. 

"  siitiafdction  with  every  exj)eriment  that  wan  made  ;  J.  C.  Hutchinson,  J. 
"  It.  JohuHon,  iiuil  J.  (i.  Alien,  of  Brooklyn ;  Elias  Marsh,  of  Patterson,  N.  J.; 
"  Nathan  Boj;eman,  J.  H.  Hunter,  G.  Durant,  F.  Delafield,  L.  Damainville, 
"  W.  M.  Ohaiuberlaiu,  J.  H.  Girdner,  Frank  H.  Hamilton,  and  E.J.  Benuing- 
"  ham,  of  New  York." 


■^W.' 


hiiiiiii 


^  jL-ljK^'tiJS^Ssaiii 


40 

"  Several  hiiiuII  Frai;iiieiith  of  Ixiiie  ewcuped  tliroiifjli  >i  fintii- 
"  Imis  <tritic(*  formed  imar  the  neat  of  the  original  wouikI. 

"  Alxiiit  eiirhtecn  months  hitcr  an  ahscess  opened  on  tlie  front 
"  of  the  (Oiest  lieh)\v  tlie  tiftli  rih  and  to  tlie  left  of  the  sternimi. 
"  Tlirou;;h  tlli^-  simis  his  K;-,r;^eon  was  altle  to  carry  a  j)rol)e  up- 
"  wards  and  liackwards  towanis  the  top  of  the  shoiihler  several 
"  inches,  and  which  sinus  was  supposed  then  to  conmumicate 
"  with  the  seat  of  the  l)a!l  on  tiie  l»ack. 

"  Pleiu'al  adhesions  were  recoj^iiized  \i\  the  medical  attend- 
"  ants  as  having  occurred  in  the  upper  part  of  the  left  thoracic 
"  cavity.  He  has  l>een  troulded  occasionally  ever  since  the 
"  injury  witli  couf:;h,  expectoration,  and  violent  palpitations  of 
"  the  heart.  A  suspicion  has  evcMi  lieen  entertained  that  the 
"  fistidous  canal  wiiich  remained  open  a  period  of  eif^hteen 
"  months,  and  then  laicame  ])crmanently  closed,  connuunicated 
"  with  tlie  hronchial  tubes,  liut  at  no  time  was  a  suspicion  en- 
"  tertaiued  Ity  him  or  his  medi(;al  atU'ndants  that  the  l>all  was 
"  jutt  lod«j;ed  in  the  !»ack  and  there  closely  encysted. 

"  We  are  disposed  to  mention  as  an  evidence  of  (Jul.  Clay- 
"  ton's  loyalty  and  faithfulness  as  a  soldier  that  within  six 
"  months  of  the  rec^eipt  of  the  injury,  and  while  the  wound  was 
"  still  discharj^ing  pus  and  Idood,  he  returned  to  active  duty 
"  with  his  regiment  .  nd  remained  in  the  field  until  the  close  of 
"  the  war. 

"  In  the  presence  of  the  gentlemen  assemhled  Col.  Clayton 
"  exposed  his  chest,  and  Prof.  Hell  proceeded  to  move  the  coils 
"  across  that  portion  of  his  Itack  where  the  ball  was  supposed 
"  to  lie  situated,  the  coUinel  indicating  the  point  underneath 
"  the  superior  angle  of  the  scapula  as  tiiat  which  had  been  fixed 
"  upon  by  himself  and  all  the  surgeons  who  had  examined  him 
"  as  its  exact  seat.  Although  being  i)uried  underneath  the 
"  scapida,  they  had  not  been  able  to  verify  their  diagnosis  by 
"  the  sense  t>f  tou('h.  Kepeated  examiiuitions  were  made  over 
"  this  region  without  any  response  both  by  Prof.  Bell  and  sev- 
"  eral  of  the  gentlemen  who  were  present. 

"  The  instrument  was  then  moved  in  every  direction  across 
"  the  ba<!k  and  shoulders  with  the  same  result.  There  was  an 
'•  evident  feeling  of  disappointment  cm  the  part  of  Prof.  Bell 
"  and  all  the  gentlemen  present,  for  no  one  entertained  a  doid)t 
"  up  to  this  moment  that  the  situation  of  the  ball  was  known 
"  and  (H)rrectly  stated  by  Col.  C/layton. 

"  It  was  not  vmtil  the  lapse  of  half  an  hoiu",  and  ;*  thorough 
"  examination  on  the  part  of  Prof.  Bell  to  determine  if  there 
"  was  not  some  iniperfec-tion  in  the  working  of  the  apparatus, 
"  that  it  was  suggested  to  move  the  instrumeut  along  the  front 
"  of  the  chest. 


immm 


A 


41 

'*  This  was  done  liy  Prof.  Hell,  tind  iniincdiately  he  exclaimed  : 
"  '  I  have  foiiiKl  it !'  And  such  was  evidently  tlie  fact,  as  was 
"  veritiiui  hy  tiie  personal  examination  tiiroiiii;h  the  telephone 
"  hy  every  fjentleman  present.  The  response  when  the  iiistrn- 
"  nient  was  moved  over  the  seat  of  the  hall  was  loud  and  liis- 
"  tinct,  and  left  no  room  for  doul»t." 

After  all  the  visitors  present  had  had  the  opportunity  of 
verifyiiifj  my  discovery  of  the  sonoro\is  spot  on  the  (rliest  of 
Colonel  (Dayton,  experimentrt  were  made  to  determine  as  accu- 
rately us  possil)le  the  exact  position  of  tlu;  hall. 

The  e.vplorinij  instrument  (Fij;.  'j;{)  was  tirst  held  over  that 
part  of  the  chest  where  the  maxinnnu  sound  was  olitained.  The 
instrtnnent  waH  then  moved  slowly  towards  the  left  until  the 
sound  <'(»ul(l  no  lonjjer  he  perceived.  Tiie  position  of  the  cen- 
tre of  the  instrument  was  noted,  and  a  verti- 
cal line  (A  H,  Fig.  27)  was  drawn  with  ink 
upon  tiie  skin  through  that  point.  This  line 
indicated  the  houndary  of  the  sonorous  area 
towards  the  left.  The  experiment  was  then 
repeated  hy  moving  the  instrument  from  the 
point  of  maximum  sound  towards  the  right, 
and  also  upwards  and  downwards,  giving  us 
the  four  Ixmndarv-lines  shown  in  the  diagram.  (Fig.  27.) 
The  hullet  was  thus  located  within  a  8<juare,  (J,  of  aI)out  one 
inch. 

"The  exact  situation  of  the  hall,"  as  descrihed  in  the  Mci- 
ical  U<i2eth\  "  was  found  to  he  witiiin  the  thorax,  prohahly 
"  in  immediate  contact  with  the  iimer  surface  of  the  rihs,  the 
"  point  heing  a  little  to  the  k^ft  of  the  steriunu,  hetween  the 
"  third  and  fourth  rihs,  and  two  or  three  inches  ahove  the  cica- 
"  trix  on  the  front  of  the  chest,  where  the  simis,  h>ng  sincie 
"  (dosed,  had  evacuated  itself,  and  in  a  direct  line  from  this 
"  cicatrix  towards  the  left  shoulder,  which  indic^ated  the  line  of 
"  the  track  of  the  original  sinus." 

Experiments  with  Needles. 

During  my  al)sence  from  Washington  and  from  all  conven- 
iences for  experimenting  personally  with  Induction  Balance 
apparatus,  I  devised  a  method  of  verifying  the  indications  of 


IM 


48 


f,n% 


r  i 


m 


tho  Iitductinii  l^ilanco  hikI  of  jwcortuiiiiiif;  tlus  oxiitit  dt^pth  at 
wliifli  a  Inillft  li(is  litMinatli  llu^  Kiirfacu.  Tliis  iimtliofl  was  cinn- 
iiuiiiicatt'd  tlir()iit;li  Dr.  Wood  ward  to  tlu;  isiir^foiiK  in  attend- 
ance oil  President  (tartield,  and  it  was  iiia<le  tli«f  siiliject  of  a 
special  paper  presented  to  the  Kntncii  Academy  of  Scieiieos 
Nov.  7,  1  SHI. 

This  metiiod,  altiimij^li  involvini;  extremely  slij^lit  pain,  would 
ordinarily  lie  used  only  as  a  preliminary  to  an  operation  for  tlieex- 
__    j,g  traction  of  a  bullet.    The 

arraiiffcment  is  shown 
in  Vh^.  -JH.  A  tiiu!  needle 
A  is  connected  to  one  ter- 
minal of  a  teleplioru!,and 
the  other  terminal  makes 
contact  with  a  plate  B, 
preferal»ly  of  the  same 
mat(;rial  as  that  compos- 
ing the  needle.  Place 
tliis  metallic  plate  B 
apiinst  the  surface  of  the 
patient's  skin  and  thrust  the  needle  into  that  portion  of  the 
l)o(ly  wliere  the  bullet  is  believed  t<»  lie  lodged.  VVMieii  the 
point  of  the  needle  makes  contact  with  the  surface  of  the  bullet 
('  a  galvanic  b;ittery  will  be  formed  naturally  within  the  iiody, 
the  two  poles  of  which  are  respectively  the  leaden  bullet  C 
and  the  metallic  plate  B.  Under  these  eircuinstances  a  click 
will  be  heard  from  the  telephoiu?  each  time  the  bullet  is 
t(»uched  by  the  needle.  This  has  been  verified  by  experiments 
upon  bullets  buried  in  a  joint  of  meat.  The  (iliek,  though 
feelde,  is  unmistakalile. 

I  have  no  doubt  that  this  method  of  exploration  ahmo,  without 
the  Induction  Balance,  would  prove  of  great  service  upon  a  field 
of  battle,  where  the  employment  of  complicated  apparatus  is 
impossible.  Mr.  Thomas  Gleason  has  recently  comminiicated 
to  me  the  jmrticulars  of  an  experiment  he  witnessed,  in  the 
<^om•se  of  which  this  method  was  trie<l  upon  a  living  subject. 
The  surgeon  who  conducted  the  experiment  was  unable  to  ob- 
tain any  response  from  the  Induction  Balance  employed,  al- 


•>mw'iweUr-M'^i^w^^*i>mmi!m^^m 


48 


thoii^li  from  (HTtriiii  indicHtioiiH  iipptirtMit  to  tlitt  koiiho  of  toiirli 
liu  Itcliovud  tliiit  tlio  l)ullut  vvHrt  Im-atiul  in  tliu|)urt  of  tliu  ImhI^ 
Buhiiiitted  to  o.\|)(M-iiii(Uit. 

To  v(^rifv  hi«Hiipp(mition  n  muddle  (^oiinwrtod  iisuhovofFlf^.  2S) 
WHS  tlinist  into  (toiituct  with  tim  iiiinl  siilistuiicti  peirtiivnd,  hut 
no  rcHponso  was  timdo  hy  thi;  tt'leplione.  Tho  nnrgeon,  how- 
'ever,  lii'lieving  that  tho  hullet  liad  hettn  found,  othtjrizud  his 
patient  and  procfoedeil  witii  an  operation,  i>nt  dineovered,  w hen 
too  hite,  that  the  bullet  was  not  there. 

FiiHlter  hfoil'ifi'dtionx  of  Imhutiou   liidance. 

I  Hailed  for  Europe  early  in  ()(!toi>er,  18H1,  and  have  had  no 
opportunity  since  of  <'ontininng  mj  researches  until  (juite  re- 
cently. While  r  was  in  Eiu'ope,  however,  Mr.  Sunnier  Tainter 
devised  a  new  kind  of  Induction  Balance  which  deserves  nien- 

F iff.  20. 


tion  here.  The  results  olitained  with  this  apparatus  in  its  pres- 
ent form  (Fig.  29)  are  not  to  he  compared  with  those  produced 
by  the  best  instnnnents  described  above,  but  there  are  undoubt- 
edly great  po,ssil)ilities  of  future  development. 


p 


u 


44 

Tli*>  iiiipiirtiuit  fttiiiiii'i!  \x  tliiit  tlu>  r.\[ili>i'iiig  iiiHtniiiiuiit  K 
(M»iini«t«  of  ft  Hhiijle  roll,  kd  that  tliere  in  no  j>os8il)ility  of  any 
part  of  tlin  exploror  ^ottiii}^  out  of  iidjiistiiu'iit.  All  tin*  ad- 
jiistinutits  arc  mado  upon  tlm  stafiotiarv  part  of  flu-  a])paratiitt. 
Till'  curnMit  of  till'  liattiTV  in  (lividml  l>i'twi'oii  two  i'(|ual  c.ir- 
(MiitH.  One  of  the  i)rimarv  circiiitH  coiitains  tlic  im>11  A  and 
tlio  t'xploriii;;  foil  K,  and  this  otiirr  ciiout  tlit)  (^)il  C  and 
a  riii'ostat  U.  Coils  A  and  ('  aro  exactly  similar;  an<l  if  the 
rcsistancii  intnxliici'd  at  \i  is  I'lpial  to  tlio  ri^sistanco  of  tin;  v,\- 
ploriiijjj  coil  K,  an  aro\i>ti(r  lialance  ran  Iid  ohtainod  l»y  the  ad- 
justnii'iit  of  the  secondary  coils  }{  I)  upon  the  primaries  A  C ; 
liiit  if  the  resistance  introduced  at  U  is  ilitTerent  from  that  at 
K,  Mr.  Taintcr  states  that  no  lialance  is  possilde. 

When  till'  i])paratus  is  adjusted   to  silence   the  ai)f)roach  of 
a  liullet  to  the  vAn\  E  destroys  the  halance. 

Althoujjh  the  j;reat  oliject  of  the  researches  that  have  been 
liroujjjlit  itefore  you  to-day  luw  been  to  find  that  arrangement 
of  halance  which  will  <leti'(rt  a  hullct  at  the  greatest  distaiiei 
from  the  coils  of  the  explorer,  it  must  not  lie  forgotten  that 
every  ease  the  instrument  is  more  sensitive  to  the  presence  o. 
liullet  plai'e<l  Inside  the  exploring  coils  than  to  one  exterior  to 
them.  When,  therefore,  we  seek  the  loi-ation  of  a  bullet  in  one 
of  the  limits,  it  nuiy  lie  ailvisidde  to  use  an  annular  coil  large 
enough  to  slip  easily   iver  the  leg  or  arm,  as  the  case  nuiy  be. 

In  Mr.  Tainter's  arrangement  the  exphiring  coil  E  (Fig  2!)) 

might  simply  be  a  large  ring  consisting  of  a  number  of  eonvolu- 

tions  of  thick  wire  which  coidd  be  slipped  over  the  limb,  or  the 

Fiq,3Q,  ring  might  consist  of    two  coils, 

^  forming    one  side  of    a  Hughes' 

Induction  Halance. 

In  either  i^ase  the  loudest  sound 
will  be  produced  when  the  bullet  is 
in  the  plane  of  the  ring,  and  its 
exact  location  should  be  deduced 
from  three  observations.  Suppose, 
for  instance,  that  with  the  ring 
inclined  in  a  particulai-  direction  the  maxinmm  sound  is  ob- 
tained when  the  ring  occupies  the  position  A  B.     (Fig.  30.) 


•h  ..f 


45 

Wo  know  then  tlmt  the  Imllct  in  in  tliiit  piano.  Now,  inclino 
tlio  riii;;  in  Konio  other  direction  lunl  exphtre  u<^iiiii.  Let 
the  position  of  niaxinaini  found  l)e  now  ('  I).  We  know 
tlien  thrtt  the  IniUet  irt  noinevvhere  on  the  Htriiififht  lino  formed 
Ity  the  intorneetion  of  the  planet*  A  li  and  C  1).  It  in  only 
noeeHHHi'y  then  to  niiike  a  tiiird  ohnervation  with  the  appa- 
ratUH  HO  inclinefj  fiiat  the  plane  of  the  rinj;  cuts  thin  Htniiji^iit 
line,  for  instance,  tln)  position  E  V.  The  i)oint  of  intersection 
of  the  three  planer  (I  is  then  the  exaet  point  occupied  hy  tlus 
l.ullet. 

i  shall  conclude  this  j)aper  hy  the  description  of  an  experi- 
ment made  in  Newport,  R.  I.,  a  few  days  aj^o.  The  results 
are  ho  unprecedented  in  my  experience  that  I  feel  they  cannot 
he  roeeived  aw  implicitly  reliahlo  until  the  experiments  luive 
heen  repeated  and  vctrifietl. 


I  had  arranji;ed  upon  a  tahle  three  coils,  (as  shown  in  Fig. 
31.)  The  large  fiat  primary  ooil  A  was  connected  with  a  hat- 
tery  of  four  Bnnsen  elements  and  an  interrupter,  as  shown, 
and  the  two  small  secondaries  of  fine  wire,  B  C,  wore  con- 
ne<!ted  with  a  telephone. 

The  secondary  B  was  moved  ahout  on  the  primary  A  until 
a  position  of  silence  was  obtained.  Upon  hringing  a  leaden 
l)ullet  near  C  the  balance  was  disturbed   and  a  distinct  sound 


i;! 


mimaiim 


*fr^yrmmmafmmmmv 


40 

produced  from  the  telephone.  There  is  nothing  very  strange 
about  this  when  we  know  that  the  distance  between  A  and  C 
was  only  15  centimetres,  so  that  0  was  well  within  the  field  of 
induction  of  A ;  hut  what  did  seem  extraordinary  was  that  the 
appi'oach  of  the  large  steel  blade  of  a  penknife  to  the  <'oil  C 
produced  no  effect !  The  iron  diaphragm  of  a  hand  telephone 
brought  close  up  to  tlie  coil  C  produced  no  sensible  disturb- 
ance of  the  balance,  whereis  a  small  disk  of  lead  produced 
quite  a  marked  effect.  A  disk  of  (lopper  the  size  of  a  tele- 
phone diaphragm  also  produced  a  good  effwit,  but  the  sound 
WIS  not  sensibly  louder  than  that  due  to  the  smallieaden  disk. 
A  diaphragm  of  zinc  o(!casioned  a  feeble,  but  distinct,  disturl)- 
an(!e  of  the  balance.  It  is  unfortunately  the  case  that  in  all 
the  forms  of  induction  balaiu-e  descril)ed  ai>ove  lead  gives  the 
poorest  effect  of  all  metals.  If  people  would  only  make  their 
ludlets  of  silver  or  iron  there  would  be  no  dithculty  in  finding 
them  in  any  part  of  the  body  !  In  the  apparatus  shown  in 
Fig.  JM,  however,  it  seems  (uf.lesH  subsequent  experiments 
sliould  reveal  some  fallacy)  that  we  have  an  arrangement  which 
is  seiisiti\e  to  lead  and  not  to  iron,  oi-,  at  all  events,  which  is 
more  markedly  intluenced  by  lead  than  iron. 

It  is  hardly  necessary  to  state  that  when  tlie  coil  C  was  re- 
moved to  a  considerable  distance  from  the  primary  A  "" 
effect  was  produced  l>y  the  approach  of  metal  to  the  coil  C. 

I  have  in  this  paper  brought  before  you  an  outline  of  a  labor 
of  love  pursued  through  mai>y  anxious  days  aiul  sleepless  nights. 
However  imperfect  or  disappointing  may  be  the  results  so 
far  achieved,  they  are  sutticiently  encouraging  to  enalde  us  to 
look  forward  witii  confidence  to  the  attainment  of  still  greater 
perfection. 

I  hope  to  contimie  these  researches  in  the  future  ;  and  cer- 
tainly no  man  can  have  a  higher  incentive  to  renewed  exertion 
than  the  hope  of  relieving  suffering  and  saving  life. 


m 


L,^*iv>  ■h^^^:})f-  Vif:^ 


3ry  8traiijj;e 
n  A  and  C 
tlie  field  of 
•ae  that  the 
the  (!oil  C 
1  telephone 
)le  disturb- 
d  produced 
e  of  a  tele- 
t  the  sound 
leaden  disk, 
let,  dibturh- 
!  that  in  all 
id  gives  the 
'  make  their 
y  in  finding 
8  shown  in 
experiments 
jTuent  which 
its,  which  is 

il  C  was  re- 
inary  A  '^" 
he  (;oil  C. 

ne  of  a  labor 
jpless  nights. 
18  results  80 
enable  us  to 
still  greater 

re  ;  and  cer- 
wod  exertion 
fe. 


APPENDIX 


Note  1.— Another  mode  of  painlesH  explorntion  snggestetl  itself  to  my  mind 
at  this  time,  bused  updu  the  fact  that  a  leaden  bullet  is  much  more  opa(iue  to 
light  than  the  substani'tis  composing  the  Iniiuiiu  body. 

I  was  aware  of  the  fact  that  the  ingenious  M.  Trouvce,  of  Paris,  had,  by 
means  of  his  polyscope,  jffoduced  a  light  inside  a  living  llsh,  and  was  thus 
enabled  in  the  <lark  to  see  the  anatomiciil  structure  of  the  tish  as  it  swam 
about  in  a  vessel  of  wat;'r. 

M.  Trouvue  had  himself  shown  me  a  modified  form  (>f  this  apparatus  for 
the  illumination  of  the  interior  of  the  human  stomach,  and  I  understood  him 
to  say  that  when  the  instrument  was  used  the  body  of  the  ))atient  (!ould  be 
seen  in  the  dark,  faintly  ilhiminated,  like  a  Chinese  lantern,  and  that  the 
extent  and  location  of  tumors  in  the  stomach  could  be  detected  (m  account  of 
their  great  ojiacity. 

It  occurred  to  me  that  leaden  ))ullet8  were  certainly  more  opaque  than 
tumors,  and  that  a  jjainless  method  of  exploration  might  be  based  upon  the 
observations  of  M.  Trouvie. 

It  would  evidently  be  impracticable,  in  the  great  majority  of  cases,  to 
introduce  into  the  Htomach  any  illuminating  apparatus ;  but  if  the  light  of  a 
projierly  prote(!ted  incandescent  platinum  spiral,  introduced  into  the  stom- 
ach, could  ))rodnce  efifeets  visible  from  the  outside— that  is,  if  this  feeble 
light  could  penetrate  through  the  Rubstance  of  one-half  of  the  body— then 
why  should  not  the  intense  light  of  an  electric  arc,  or  of  a  lime  light,  pene- 
trate the  whole  body  from  one  side  to  the  other  so  as  to  produce  similar 
effects? 

The  most  feasible  plan  that  occurred  to  me  v.'ns  to  place  an  electric  lamp 
at  one  end  vi  a  long  opaque  tnV)e,  and  to  apply  the  other  end  closely  against 
tlw  skin  of  the  jiatieut.  The  interior  of  the  t)ibe  between  two  plate-glass 
diai)hrrtgm8  could  be  filled  with  a  saturated  solnticm  of  alum,  or  some  f)ther 
higlily-absorbent  transparent  substance,  so  as  to  obstruct  the  passage  of  heat 
rays. 

Of  course,  the  whole  ai)paratns  was  to  be  so  arranged  that  no  light  from 
the  lamp  could  escape  into  the  room  to  interfere  with  the  experiment. 

Under  these  circumstances,  the  body  of  the  patient,  or  at  least  a  portion  of 
it,  should,  in  a  dark  room,  ai)pear  self-luminous;  and  it  seemed  i>t)ssible  that 
the  shad(,w  of  au  imbedded  bullet  might  be  projected  up(m  the  skin.  The 
track  of  the  bullet  might  also,  perhaps,  be  discernible  as  an  illuminated 
streak  either  more  or  less  bright  thai\  the  surrounding  surface. 

These  consideratitms  led  me  to  try  i).  number  of  experiments,  which  proved 
that  the  method  was  feasible  where  the  bullet  was  very  near  the  surface  of 
the  body.  On  account  of  the  great  and  irregular  refraction  of  light  in  jiass- 
ing  through  the  tissues  of   the  body,    I   doubt  whether    the    shadow  of    a 

47 


•M 


48 

<l(M'iily-s('iit('(l  Hiimll  Imllt't  could  1«'  (1iHtiii){niHliii1>Io  upon  the  Hkiii,  uiiIchh, 
iiiilcfil,  u  vt'ry  lirilliuiit  liKht  <>munutiu){  from  ii  Hinglu  poiut  could  be  Hitfuly 
])roduct'd  iimidti  the  body, 

The  following  <'X|)('rim('iitH  ("iiriiiK  ujjoii  thr  Hubjfct  were  umdc  in  KuHton 
July  fith,  IMHI,  with  the  iiKHiHt  iiicc  of  Mr.  Wni.  Schuyh  r  JoIiuhoii: 

Mrprriniint  1.  -  Mr.  JolniMcn  pliK^ttd  in  Iuh  mouth  n  ^Iiihs  cylinder  ooi>tjv»n- 
iiiK  II  H))iriil  of  |iliitiiiuni  wire,  which  Wiis  rendered  inciiudeHCcnt  by  th''  piiHS- 
iif{('  of  III)  electrical  current.      He  also  held  in  his  cheek  ii  HiiiiiU  leiiden  bullet. 

In  II  diirk  room  the  eflfect  was  very  striking.  The  cheek  u|)j)eiire<l  seiui- 
triumparent,  and  the  location  of  the  bullet  was  detected  at  a  glance  by  a 
shadowy  spot  upon  the  skin. 

Kxpiriiin'iit 'i.-'K  nietuUic  glove  l.uttou  fnot  more  than  4  or  .'>  mm.  in 
diameter)  was  attuclied  to  the  glass  cylinder  by  a  few  turns  of  black  thread 
jiassed  round  the  cylinder. 

In  this  case  the  effect,  although  not  so  marked  as  in  the  former  experiment, 
was  cpiite  discernible,  and  a  faint  shadowy  streak  could  be  seen  crossing  tho 
cheek,  caused  by  the  Hhnthiw  of  the  bhick  thread  tied  rouu<l  the  cylinder. 

Note  2. --///■<<«'/•  ffcm    Mr.  (Uimfi-  M.  Ilupkinx,  puhliHhfd  in  the  New   York 

rrihuin;  July  11,  1«81. 

LKTTEllS    FIIOM    THE   PKOPLE — THE    DTIla.ET    FIKEU    IIV    OTHTEAtl. 

A  miggcHfion  tl  "t  the  I  miction  Halancf  he  lined  to  dinnm-r  itx  pmtioa  in  the 

I'rexiilent'M  txidy. 

To  the  Kdit^i}'  iif  thf  Trilnine : 

SiK:  The  atteni]>t  ui)ou  President  (lartield's  life  and  the  present  condition 
of  the  sufferer  have  called  forth  the  nation's  deepest  sympathies,  iiud  elicited 
very  many  suggestions  as  to  the  metlnxls  of  promoting  his  comfort  and  assur- 
ing his  recovery. 

As  one  crisis  aft<'r  another  has  jmssed  ho))e  has  risen,  and  the  people  wait 
with  earnest  desire  for  the  last  danger  to  pass  away. 

The  attending  and  consulting  surgeons  state  that  it  is  impossible  to  predict 
he  final  res\ilt  of  the  shot  without  locating  the  ball. 

With  all  deference  to  the  several  methods  proposed,  I  desire  to  suggest  a 
method  of  ascertaining  the  position  of  the  missile  which  will  be  painless  and 
harmless,  aiid  which,  in  my  experiments  under  conditions  analagous  to  those 
under  wliich  it  might  be  practised  in  the  ))resent  instance,  has  proved  suc- 
cessfiil.  I  rt  I'er  to  the  use  of  the  Induction  Balance— a  most  delicate  elec- 
trical instrument  for  detecting  the  presence  of  m.tnls  —a  modified  fonu  of 
which  coidd  be  easily  ajjplied  in  this  case  with  a  reasonable  expectation  of 
success.  This  instrument  ccmsists  of  two  short  glass  cylinders,  around  each 
of  which  are  wound  two  parallel  coils  of  tine  insulated  cojiper  wire. 

One  coil  of  each  pair  is  included  in  a  battery  circuit,  in  which  there  is  .i 
clock  micro])hone.  The  other  p.iiir  is  placed  in  a  closed  circuit  with  a  receiv- 
ing teleiihoue.  The  two  gloss  cylinders,  with  their  encircling  coils,  may  be 
widely  sf^parated. 

The  induction  set  up  in  the  secondary  or  telephone  circuit  is  balonced  by 
the  reversal  of  one  of  the  r.econdary  coils,  and  so  adjusted  that  the  induction 


mi 


49 


in,  iiulcHS, 

1  l)e  wifely 

in  H*>8toQ 
Br  contrm- 

f  the    J)11H8- 

Icn  bullet, 
iired  seuii- 
lanee   liy  a 

'  f)  mm.  in 
ack  thread 

'xperiment, 
Tossing  the 
yliuder. 

Jfew   York 

AU. 

sition  ill  the 


nt  cou(litii)n 
ami  elicited 
ft  uud  ttBsur- 

people  wait 

rle  to  predict 

to  suggest  a 
painless  and 
j[ous  tt>  those 
proved  snc- 
lelicate  elec- 
ifled  form  of 
xjjectfttion  of 
around  each 
,iri'. 

ch  there  is  a 
with  a  receiv- 
coils,  may  be 

)  balanced  by 
the  induction 


in  one  of  the  seoondary  coils  exactly  balanfjes  or  neutralizes  the  induction  in 
the  other,  so  that  when  the  ^ar  is  applied  to  the  receiving  telephone  no  sound 
is  *eard. 

Now,  by  placing  ever  so  small  a  piece  of  met4il  in  one  ;»f  the  glass  cylinders, 
the  electrical  balance  is  disturbed  and  the  clock  ou  the  microphone  is  heard 
to  tick  loudly,  thus  indicating  the  presence  of  metal,  and  the  siuue  is  true  if 
the  coil  be  placed  in  the  vicinity  of  a  piece  of  metal. 

It  occurred  to  me  to  try  the  effect  of  a  lead  bullet  upon  the  instrument, 
placing  it  at  different  distances,  and  separating  it  from  the  coil  by  insulating 
material.  The  result  exceeded  my  anticipations,  as  with  o  set  of  coils  that 
were  by  no  means  sensitive  I  vim  able  to  locate  the  bullet  with  the  coils  raised 
a  vertical  distance  of  nearly  two  inches.  With  more  sensitive  apparatus  it  is 
more  than  probable  that  the  bullet  might  be  located,  even  though  distant 
several  inches,  by  passing  a  pair  of  coils  over  the  President's  back  and  abdo- 
men ;  and  by  comparative  tests  the  depth  of  the  bullet  might  be  ascertained. 

GEORGE  M.  HOPKINS. 
Brooklyn,  July  10,  1881. 

Note  ^.—Letter  from  Mr.  G.  M.  Hopkim  to  Private  Secretarj/  Brown,  en- 
ehmiig  printed  deiuiription  of  Hugheif  Induction,  Balance. 

Office  of  the  Scientific  Amebican,  No.  37  Park  Row, 

New  York,  July  IIW,  1881. 
Mr.  J.  Stanley   Brown, 

Executive  Manxion,  Washington,  D.  C: 
My  Dear  Sib  :  I  send  herewith  a  full  description  of  the  Induction  Balance 
as  promised  in  my  note  of  yesterday.     I  will  send  the  appnritws  for  trial  if 
desired. 

I  am  certain  that  the  bullet  can  be  located  with  it  if  it  ih  not  too  deeply 
seated. 
Please  advise  Dr.  Bliss. 

Very  respectfully, 

GEO.  AI.  HOPKINS, 

Of  the  Seientijic  A  'nrriean. 

Note  4:.— Letter  from  Mr.  Oe/).  M.  Hopkim  to  Private  Secretary  Brown  ae- 
companyiug  the  Hughes'  Induction  Balance  apparatus  he  fmearded  to  the 
Executive  Mansion  for  trial. 

CO  Irving  Place,  July  lUh,  1881. 
Mr.  J.  Stanley  Brown  : 

Dear  Sir  :  I  give  beh)w  a  few  suggestions  in  regard  to  the  use  of  the  In- 
duction Balance  sent  herewith. 

Very  respectfully, 

GEO.  M.  HOPKINS. 

Suggestions :  Connect  A  to  A,  B  to  B,  Ac. ,  as  marked  on  the  wires.  Strength 
of  current  used,  15  or  20  volts. 

A  strong  current  extends  the  influence.  Use  the  clock  interrupter,  and 
place  a  drop  of  mercury  in  the  vulcanite  cup  to  make  connection. 


WtHtlliMiiimmk 


50 

The  coilH  lire  uow  ftrljnsted  to  "silence,"  but  will  probably  have  to  be  re- 
rtdj-istod  ..11  their  arrival  iu  Washington;  as  a  iJ„  inch  movement  of  one  of 
the  coils  %vill  throw  it  out  of  aajustment,  it  will  be  seen  that  the  adjustment 
is  a  matter  of  great  nicety.  Tw(»  telephone  receivers  should  be  employed, 
and  the  most  acute  sense  of  hearing  is  roquired  to  distinguish  the  ticking 
when  the  ball  is  two  inches  distant  from  the  coils. 

Tlie  shorter  instrument  is  intended  for  application  to  the  patient  should  it 
be  considered  suffieieutlv  sensitive  to  warrant  the  experiment. 

Asa  prelhni'W.-,' experiment  pass  the  Induction  Balance  over  the  pocket 
containing  coins,  "keys,  &c.;  also  over  buttons,  buckles,  &c.,  attached  to  the 

garments.  , 

Lead  is  the  poorest  of  all  metals  to  locate  with  this  instrument.  If  the 
ball  were  of  iron  it  could  be  readily  found  at  a  distance  of  3  or  4  inches. 

■  Yifym  5.— Telegram  fro7n  Prof.  Neiwnnb. 
•  Executive  Mansion, 

Washinqton,  D.  0.,Jidy  VMh,  1881. 
To  Prof.  A.  G.  Hell, 

Care  of  Chan.  Williams,  109  Cmirt  nt,  Jionton,  Mam.: 
Perhaps  smtiU  core  for  coil  no  larger  than  bullet,  with  very  flue  wire,  mi^ht 
give  best  effect.     Shall  telegraph  to  Rowland  to  know  best  theoretical  form. 
Telegraph  me  or  Brown,  care  Executive  Mansion,  what  train  >'""/"'',''• 

Note  Q.— Telegram  from  Prof  John  TrowMd^e. 

Bar  Habbor,  Maine,  Jiili/  Idth. 
To  Secretary  Brown, 

White  Home.  Waxhington,,  D.  C.,for  Prof  Bell: 
Make  resistance  of  secondary  coils  equal  to  telephone.     Put  large  number 
of  turns  of  wire  on  primary  and  secondary  coils.     Primary  coils  long  com- 
oared  with  width.     Put  secondary  coils  aroui  j.  middle  of  primary  coils. 
^  .    ,  JOHN  TROWBBIDGE. 

Note  1. -Telegram  and  letter  from  Prof  Rowland  U>  Prof  Neweomb. 

Hunter,  N.  Y..  July  Uth,  1881. 
To  Prof.  Simon  Newcomb, 

Executive  Manxion,  Washington,  D.  C: 
Telegram  just  received.     Mak.  ...res  four  inches  long,  with  six  layers  of 
number  twentv  wire;   diameter  an  inch  and  one-half.     Make  outer  coil  half 
an  inch  wide  aud  half  an  inch  thick,  of  ftuest  wire,  and  slip  over  inner  coil  at 
its  end.  jj    f^    ROWLAND. 


■      '  Letter  following  above  telegram. 

Hunter,  July  14,  '81. 

^  DEAH^Sw°*When  your  telegram  arrived  I  had  gone  to  the  Hotel  Kaaters- 
kiU.  about  ten  miles  from  here,  to  stay  over  „   ;Ut.     The  telegram  was  sent 


61 

back  to  the  office  to  be  seut  to  me,  and  luy  friniKls  thotight  that  I  hiid  received 
it ;  but  the  stupid  luiin  here  Biinply  kept  it  uud  would  not  send  it,  becnuse  lie 
had  no  authority  to  send  it  further. 

I  have  telegraphed  back  a  reply.     The  dimensiouH  should  probably  be 
about  as  follows : 


Six  Itxtferm  t^Xo.  £0»oirB . 


--4tne?i0a- 


^ 


■J-  ^ftc/t, 
square-. 


Of  course,  the  two  must  be  precisely  alike,  and  the  induction  coefficients 
of  one  should  be  made  t«  vary  by  ri  screw,  which  would  move  one  of  the  sec- 
ondary coils  nearer  to  or  further  from  the  end  of  the  primary. 

Yours  truly, 

•       HENKY  A.  ROWLAND. 

P.  8. — For  these  dimeusions  a  telephone  with  many  turns  of  fine  wire  in  its 
coil  would  be  best. 


Note  8. — Comviunicatwrm  with  Prof.  I).  E.  Hughes,  of  London,   England, 

(a.)  Cablfgram  to  Mr.  Preeee,  Superintendent  Postal  Telegraph,  London, 

England. 

Washington,  July  15M,  1881. 

To  Prkece, 

London:  y*r     ^"^ 

Can  Hughes  suggest  form  of  Induction  Balance  to  locate  leaden  bullet  in 

President  ?    If  bo,  cable  at  my  expense, 

GRAHAM  BELL. 


mmmtm 


MaiAaaMMM4MiMtd<akliiUMlkiwU 


52 

(A.)  Tdegraphie  reply  to  ab<rve. 

Whitney, 

WaMngton,  D.  C. : 
Preece  siiyg  t(i  Graham  Hell,  Washington  :  "  Interesting  and  hoiiefnl  letter 
from  Hughes  with  diagraius  Bent  you  to-day." 

W.  GREEN, 
Pren.  We»t.  Union  Tdegrnjih  Co. 


(c.)  NoU  from  Mr.  Preece  eneUmng  letter  from  Prof.  Hughes. 

Qenekal  Post  Office,  London,  England,  11)  July,  1881. 
My  Dear  Beli,  :  The  enclosed  very  interesting  letter  from  Hughcm  will 
enable  you  to  make  some  experiments,  which  I  trust  will  result  in  success. 
Yours,  sincerely, 

W.  H.  PREECE. 

Prof.  AiiEXandeb  Gbaham  Bell, 

WiUihington,  D.  O. 


id.)  Prof.  Hughes  to  Mr.  Preece. 

108    Gt.    POIITLAND    STEEET,    W.    LoNDON,    Jllly  IWl,    .S81. 

Dear  Preece:  In  reply  to  yours  of  to-ilay  enclosing  telegram  from  Pi  of 
Graham  Bell,  I  believe  a  specially-constructed  Induction  Balance  could  be 
made  to  locate  the  leaden  bullet  in  President  Garfield,  provided  the  ball  was 
nearer  to  one  side  of  his  body  than  the  other. 

Suppose  we  have  two  flat  superposed  coils  on  a  single  reel,  so  that  these  t'^'o 
coils  form  a  single  one  as  regard  their  relative  distance  ;  these  coils,  if  con- 
nected with  the  usual  adjusting  coils  of  ray  balance,  could  be  reduced  to 
silence;  then,  on  moving  these  coils  near  a  metallic  bccly,  sounds  would  be 


nattery 


J^rwuxry  rails 


heard.  Thus  the  only  difference  would  be  instead  of  as  usual  taking  the 
metallic  body  to  the  coils  upon  a  fixed  table,  we  take  the  coils  to  a  fixed  body 
in  which  we  suppose  metal,  such  as  a  bullet,  to  V)e  hid. 


58 


Now,  suppose  we  take  the  coils  A  and  move  it  over  a  body  with  a  bullet, 
thus: 


sful  letter 


5N, 
nph  Co. 


fien. 

/,  1881. 
igbes  will 
nfcess. 

lEECE. 


/(,  .S81. 

rom  Pi  of 

could  be 

e  ball  was 

;  these  tvo 
ils,  if  con- 
educed  to 
t  would  be 


taking  the 
fixed  body 


If  bullet  near  C,  we  should  Ijear  it  when  coils  just  above  it ;  at  E,  when  the 
coils  wcvo  btdow ;  but  if  bullet  iu  the  centre  of  the  body,  then  we  should  have 
equal  or  probably  no  indications. 

All  this  could  be  most  easily  done  and  with  some  results  if  the  bullet  had 
been  of  copper  or  silver,  but  lead  has  such  a  high  resistance  and  gives,  con- 
sequently, very  feeble  tones. 

We  can  easily  hear  a  copper  penny  at  some  inches  distant  from  the  coils, 
but  lead  requires  that  it  should  not  be  more  than  one  or  two  inches  distant ; 
con8e(pieutly,  more  sensitive  coils  woiild  be  required  or  a  larger  battery. 

I  th-nk  the  experiment  a  hopeful  one,  and  above  all  that  the  coils  are  easily 
madi,  and  simple  exi)eriment8  could  be  first  made  to  find  a  bullet  in  a  mass  of 
cotton,  Ac. 

The  microphone  is  invaluable  as  a  pro))e  for  bullets.  I  made  the  first  for 
Sir  Henry  Thomson  to  find  out  st(me  in  blud  der.  But  it  is  even  more  applicable 
to  bulleis.  It  consist*  of  a  simple  hammer  and  anvil  mieroph(me  adjusted 
upon  the  handle  of  the  ordinary  probe.  The  instant  this  i)robe  touches  any 
hard  substance  a  loud,  sharp  click  is  heard  in  the  telephone.  The  smallest 
shot  can  thus  be  heard,  and  there  is  a  very  distinctive  tone  between  when  the 
probe  strikes  a  bone  or  bullet.  This  instrument  is  well  known  to  surgeons,  so 
I  need  not  say  more  about  it. 

If  you  write  to  Prof.  Bell,  please  enclose  this,  as  I  should  be  pleased  to  hear 
of  his  success. 

Sincerely  yours, 

W.  H.  Pbkbce,  F.  R.  8.  ''•  ^-  «U«™«- 

Note  9.— Letter  from  Mr.  Oharle»  E.  Buell  to  Col.  Rockwell. 
Col.  Rockwell  : 

Dear  Sir  :  Please  suggest  for  me  that  in  an  electrical  test  to  locate  the  bul- 
let it  will  only  be  done  with  certainty  by  obtaining  a  balance,  which  can  be 
done  as  follows:  When  the  loudest  tick  is  obtained  by  placing  the  inducing 
coil  in  the  vicinity  of  the  imbedded  bullet,  then  move  another  bullet  of  eciual 
size  towards  the  other  coil  of  the  bridge  until  a  balance  is  had  and  no  tick  is 
audible,  when  the  imbedded  bullet  will  be  known  to  be  a  like  distance  from 
its  respective  coil. 

CHARLES  E.  BUELL, 
Electrical  Engineer,  Hew  llaxsen,  Conn. 


'■' --'"■"■  ■-■-"  >=?  '  ■  i^rY-^flf^^lrif-' •; 


54 

Note  \Vt.—N»U  frmn  l>r.  Vhif,he»ter  A.  Btll. 

N    Y    CkNTBAL  U.  It.,  BETWEEN  aVBAOUBB  AND  BCFFALO, 

July  16W,  1881. 

Dear  A  «  B.-.  If  your  coilH  are  syiumetrioally  iirrunged,  should  it  not  be 
posHible  to  bulauc.  the  effcet  of  a  bullet  on  one  side  by  a  bullet  placed  m  5 
correBponding  iwsitiou  on  the  other? 

Probably  you  have  thought  of  this  before,  but,  if  not,  it  may  be  worth  a 

three-cent  stamp. 

Youth,  tnxly,  CHICHESTER  A.  BELL. 

Note  W.—Note  and  telegram  from  Mr.  J.  H.  C.  Watt*. 

Balto.,  July  21#<,  1881. 

Prof.  A.  Graham  Bew., 

1221  Conn.  Ave.,  Waxfiingtim.  D.  C: 
Am  working  hard  at  our  problem.     Hucoeeded  in  reaching  full  three  inches 
last  night,  but  owiTig.  I  think,  to  my  battery  weakening  somewhat,  can  hardly 
reach  so  far  now.    V.n't  you  please  advise  me  how  you  are  getting  along, 

and  oblige,  , 

Yours,  very  truly.  j.  h.  C.  WATTS. 


f 


Telegram. 

Baltimobe,  July  23d,  1881. 

Prof.  A.  G.  Beli-, 

WanMngton,  D.  C: 
Have  been  umible  to  obtain  satisfactory  results  since  first  trial,  and  prob- 
ably yours  is  at  least  as  good  as  mine.  j    H.  0.  WATTS. 


Note  n.— Letter  to  Dr.  Bli»». 

VoLTA  Labobatobt,  1221  CoNNEcnctrr  aventje, 

Washington,  D.  C,  July  23,  1881. 

Db.  Buss, 

Executive  Mandon : 
My  Dear  Sir  :   You  were  kind  encmgh  to  suggest  that  preliminary  experi- 
ment«  should  be  made  with  the  Induction  Balance  upon  the  person  of  Lieu- 
tenant Simpson,  whose  address  you  gave  me.     I  accordingly  communicated 
with  the  lieutenant,  and  he  came  to  my  laboratory  hvst  night  in  company 

with  Dr.  Stanton. 

The  new  instruments  we  had  hoped  to  use  were  not  complete,  so  we  had  to 
content  ourselves  with  the  apparatus  you  tested  the  other  day. 

Upon  passing  the  coils  over  the  back  of  the  lieutenant,  it  was  found  that 
at  one  spot  a  feeble  sound  made  its  appearance-too  feeble,  however,  to  be 
entirely  satisfactory  as  evidence  of  the  presence  of  a  ball.  I  find  that  very 
feeble  sounds  Uke  that  heard  are  easily  conjured  up  by  imagination  and  expe<v 
toncy  but  the  following  facts  seem  to  indicate  that  in  this  case  the  -ound 


55 

wan  (l\ii>  to  an  external  cause — probably  to  the  presence  of  a  very  deeply-im- 
bedded Imllet : 

1.  The  Hound,  although  it  could  not  always  be  dinting uished,  uniformly 
appeared,  when  audible,  at  tlte  name  uptit. 

2.  It  was  heard  independently  by  Mr.  Tainter,  Dr.  Stanton,  and  myself  at 
the  same  spot.  (If  I  recollect  rightly,  the  lieutenant  himself  also  located  the 
sound,  but  iiiy  father  could  hear  nothing.) 

3.  A  blindfold  test  was  then  made.  Mr.  Tainter  closed  his  eyes  and  turned 
away  while  the  coils  were  moved  over  different  parts  of  the  lieutenant's  back. 
The  moment  the  sonorous  spot  was  covered  Mr.  Tainter  declared  he  could 
hear  the  sound.  We  are  to  rejjeat  the  ex]>eriments  with  our  new  instrumentB 
as  soon  as  they  are  completed,  and  I  shall  report  progress. 

Yours,  truly, 

ALEXANDER  GKAHAM  BELL. 


Note  13.— Letter  to  Dr.  BUm. 

Wa8hinoto:j,  ./«iy  27«A,  1881. 
Dr.  Bliss: 

My  Dear  8ib  :  Permit  me  to  make  a  few  remarks  upon  the  value  cI  the 
indications  of  the  Induction  Balance  in  determining  the  location  of  a  lead 
bullet  imbedded  in  the  human  body. 

Podtive  deduction*  eoneeming  the  lor/ition  of  the  ball  can  only  he  mifely 
made  from  positive  indieMi^in^  of  itn  pre»enM.  Negative  indication*  may 
tnean  anything. 

For  instance :  If  we  hear  a  sound  from  the  telejihone  connected  with  the 
balance  every  time  the  exploring  coil  is  passed  over  a  certain  part  of  the 
body,  this  may  b»i  taken  ns  proof  positive  that  a  metallic  mass  is  to  be  found 
in  the  neighborhood  of  the  sonorous  spot.  If,  on  the  other  hand,  we  fail  to 
obtain  audible  effects,  we  are  not  entitled  to  conclude  that  the  bullet  is  absent 
from  the  part  explored,  or  that  it  is  imbedded  ut  a  greater  distance  below  the 
surface  than  the  i)enetrating  distance  of  the  instrument  used,  for  the  bullet 
may  be  witliin  any  part  of  the  area  explored  and  close  to  the  surface  without 
afflicting  the  balance  if  it  is  flattened,  and  if  it  is  so  located  that  the  i)lttne  of 
its  face  is  nearly  perpendicular  to  the  plane  of  the  face  of  the  exploring  coil. 

A  few  words  may  not  be  out  of  place  here  concerning  the  experiment  made 
lost  night  ujion  the  person  of  the  President. 

Before  entering  the  President's  room,  I  applied  the  telephone  to  my  ear, 
and  heard  a  peculiar  spluttering  sound  which  it  was  found  impossible  to 
extinguish  by  any  adjustment  of  the  coils.  I  satisfied  myself,  however,  that 
the  arrangement  was  in  a  sensitive  condition,  by  holding  near  it  a  flattened 
bullet.  The  hearing  distance  appeared  to  be  about  4  cm.  When  the  explor- 
ing coil  was  passed  over  the  back  of  the  President  near  the  spine,  no  definite 
pulsation  of  the  sound  was  heard ;  but  when  the  coil  was  first  passed  over  a 
portion  of  the  front  part  of  the  abdomen  near  the  right  side,  I  heard  at  one 
point  a  shaqj  and  sudden  reinforcement  of  the  sound.  Upon  moving  the  coil 
backwards  and  forwards  a  number  of  times  over  the  same  spot,  I  was  unable 
to  verify  the  observotiou.    I  should  state  here  that,  when  a  perfect  balance  is 


5« 

nut  ubtniutui,  it  in  not  mifo  to  plitco  reliituco  upon  a  Hingle  obsorvfttion  of  u 
piilHiition  in  the  sound,  iw  n  Kiuiiliir  cffoct  might  ha  eiuiHud  hy  an  aoi-iclcntal 
irregularity  in  the  vibration  of  the  iuHtrunicut  iwed  to  intemipt  the  eleotrioal 
current. 

The  Hoiind  heard  was  dintinct  and  well  marked,  but  it  wotild  not  be  safe  to 
ccmcludo  that  it  was  due  to  the  prcr"  e  of  the  bullet,  unlesH  the  effect  could 
be  rci)ro<lucod  a  number  of  timeB  and  alwayn  at  the  Hanie  Hpot. 

I  tliiuk  I  meutioned  to  you  that  it  was  diHcoverod  yesterday  morning  that 
the  ap))li('atiou  of  a  tin-foil  "coudeUHer"  to  the  luduetiim  lialance  markedly 
influenetid  the  hearing  diHtauee,  inereaHiug  it  in  our  experinieuUi  by  about  one 
centimetre. 

A  eondenner  waH  therefore  em- pcted  to  the  arrangement  uwd  last  night, 
but  it  has  siu(!e  been  found  thai  the  eondeuHer  waH  only  couuected  to  one  side 
of  tile  l)alance,  instead  of  to  both.  This  mistake  is  enough  to  account  for  the 
difficulty  experienced  in  adjusting  the  coils  so  lUi  to  obtain  an  acoustic  bal- 
ance, and  for  the  observed  reduction  in  the  hearing  distance. 

If  it  is  of  importance  to  locate  the  bullet  at  once,  I  would  recommend  an 
immediate  repetition  of  the  experiment  with  the  condenser  properly  arranged. 

Whatever  other  results  might  be  obtained,  I  feel  sure  we  could,  at  all 
eventj*,  settle  immediately  whether  the  sound  I  heard  was  due  to  the  presence 
of  the  bullet  or  was  an  accidental  phenomen(m. 

If  it  is  not  important  to  locate  the  bullet  at  the  i)resent  time,  it  might  be 
well  to  jxistpone  a  repetition  of  the  experiment,  so  as  to  give  Mr.  'fainter  and 
myself  more  time  to  improve  our  ap]>aratus. 
Yonra,  triily, 

ALEXANDER  OUAHAM  BELL. 


Note  li.— letter  to  Dr.  Blm. 

VOLTA    LaB0B*TOBY,    1221    CoNNECTnCUT   AVENUE, 

Washimoton.  D.  C.,July  31,  1881. 

My  Deab  Dk.  Bliss  :  I  write  to  let  you  know  that  my  new  form  of  Induc- 
tion Balance  gives  brilliant  promise  qI  success.  The  indications  with  a  flat- 
tened bullet  are  well  marked  and  distinct  at  a  distance  of  three  inches,  and 
audible  effects  can  even  be  diHtinguished  at  five  inches,  but  beyond  three 
inches  silence  and  the  greatest  attention  are  requisite.  Effects  are  produced 
at  about  two  inches,  when  the  bullet  is  held  with  its  edge  towards  the  instru- 
ment— a  position  that  gave  no  results  with  our  former  apparatus. 

.Vltogether  I  feel  v(!ry  much  encouraged.  The  apparatus  in  its  present  form 
is  a  very  clumsy  affair,  the  surface  that  would  be  applied  to  the  person  of  the 
President  measuring  seven  inches  by  four.  I  hope  to  reduce  the  size  of  the 
apparatus  very  greatly  in  a  day  or  two.  In  the  meivntime,  should  any  neces- 
sity arise  for  an  experiment  upon  the  President,  we  have  much  better  chances 
of  success  than  at  any  previous  time. 

Yours,  very  truly, 

ALEXANDER  GRAHAM  BELL. 


vfttion  of  a 

10  (vluctrical 

t  be  Wife  to 
affect  could 

>rning  that 
e  iimrkedly 
y  about  one 

InHt  uight, 

to  out'  Hide 

lunt  for  the 

:ouHtic  bal- 

>niniend  an 
ly  arranged. 
:iuld,  at  all 
he  presence 

it  might  be 
Taiuter  and 


VI  BELL. 


BNUE, 

'31,  1881. 
oa  of  Induc- 
)  with  a  flat- 
iucheii,  and 
Byond  three 
re  produced 
s  the  instru- 

iresent  form 
erBon  of  the 
9  size  of  the 
1  any  ueoes- 
tter  chances 


M  BELL. 


57 

Note  16.— /w«<^r  t>i  Dr.  /«»**. 

VOLTA    LaBOHATORV,    1221    (JoNNECnCUT   AVKNVK,      . 

Wahhinoton,  I>.  C,  July  Ml,  1881. 
Dr.  BuHH, 

K/ecutirf  Mannnn : 

Dear  Hi  We  have  made  ex|)eriniPutH  this  evouing  upon  the  |M>r(ioti  of 
I'rivate  .lohu  Mcdill,  an  old  solilii^r,  who  was  wonndeil  at  tlu<  battle  of  Oaiues' 
Mill,  iu  1SG2,  and  who  still  carries  the  ball  that  shot  him. 

I  found  no  difficulty  in  flndiug  a  sonorous  spot  in  his  back,  when'  undoubt- 
edly tlm  bullet  lies  imbedded. 

Mr.  Taiuter  also  located  the  Imllet  in  the  same  place.  Upon  pressing  with 
the  flugers  uiion  the  Hi>ot  a  lnm|>  coulil  be  felt  between  two  of  the  riVis.  We 
experimented  ujMm  this  same  man  yestenlay,  using  a  similar  form  of  Induc- 
tion Balance  to  that  we  tried  upon  the  person  of  thi^  President  the  other  day, 
but  could  obtain  no  indications. 

The  new  form  of  Induction  lialance  is  so  sensitive  that  a  new  difficulty  is 
intnMluced  by  the  effects  produced  by  large  iiietnllic  masses— for  instinco, 
gas  lustres,  iron  flre-jjlaces,  Ac. 

I  think  also  that  the  earth's  mivgnetism  affects  the  result.     We  shall  inves- 
tigate these  causes  of  disturbance  to-night. 
Yours,  sincerely, 

ALEXANDIilt  (HtAHAM  BELL. 

Note  16.—Ht>port  to  the  mirgeom  publinhed  in  the  daily  jtapern  Aug.  2,  1881, 

VoLTA  Labobatorv,  1221  (!oNN.  Ave., 

Washington,  1).  C,  Aug.  \»t,  1881. 
To  the  Hurgeong  in  nttendnnee  upon  Prenident  Oarfleld  : 

Gentlemen  :  I  beg  to  submit  for  your  information  a  brief  statement  of  the 
results  obtained  with  the  new  form  of  Induction  Balance  in  the  experiments 
made  this  morning  for  the  purjiose  of  locating  the  bullet  in  the  person  of  the 
President.  The  iustrumeit  was  tested  for  sensitiveness  several  times  during 
the  course  of  the  experinHsuts,  and  it  was  found  to  respond  well  to  the  presen- 
tation of  a  flattened  bnllei;  at  a  distance  of  aliout  four  inches  from  the  coils. 

When  the  exploring  coils  were  passed  over  that  part  of  the  abdomen  where 
a  sonorous  spot  was  observed  in  the  experinieuts  made  on  July  2(;tli  a  feeble 
tone  was  perceived,  but  the  effect  was  audible  a  considerable  distance  around 
this  spot.  The  sounds  were  too  feeble  to  be  entirely  satisfactory,  as  I  had 
reason  to  expect  from  the  extreme  sensitiveness  of  the  instrument  a  much 
more  marked  effect.  In  order  to  (vscertain  whether  similar  sounds  might  not 
be  obtained  in  other  localities  I  explored  the  whole  right  side  and  back  below 
the  point  of  entrance  of  the  bullet,  but  no  part  gave  indications  of  the  presence 
of  metal,  except  an  area  of  about  two  inches  in  diameter,  containing  within 
it  the  spot  previously  found  to  be  sonorous.  The  experiments  were  repeated 
by  Mr.  Tainter,  who  oVitained  exactly  corresponding  results.  We  are  therefore 
justified  in  concluding  that  the  ball  is  located  within  the  above-named  area. 

In  our  preliminary  experiments  we  found  that  a  bullet  like  the  one  in  ques- 


^.>«...>„.^.«:.,-,.«.-J.,.i,A-.,^     ^^.-a  ..,,„.■.,,),,,    ,^.^.^^yi^_-i,.    .^-.-^^.■■^_ 


tioii  wht'ii  in  itM  luiniiiil  Hhupr  prixlucfd  noimdiliU'  flTect  Im^vkuiI  u  iliHtuncii  of 
twii  mill  Ik  lii.lf  iiK'lu'M,  while  the  Hikiiit>  Imllft,  Hiittfiicd  niiil  priMciitcd  uitli  iU 
fuel'  purikllcl  Id  tlic  \i\,nu>  iif  the  c'iiIIh,  kuvi'  iniliriitioim  up  tun  (1iHt»uc«>  of  five 
illcheM.  The  Hiiliie  Hatteiieil  hullet,  helil  with  itN  fitce  per|H'li<liculikr  to  th(t 
pliuiu  of  the  coilH,  prixlueed  no  houikI  hevond  u  diHtnuee  of  one  inch.  Tim 
fiictH  hIiow  thiit,  in  iKnoriince  of  the  netiiiil  Hlmpe  iind  mode  of  jjrettentution  of 
the  liullet  to  tho  exploring  inHtninient,  thi'  ilejith  iit  whieh  the  bullet  lieH  Iw- 
ncath  tho  Hurfuco  ejinnot  lie  iletenniued  from  our  expeiimeutH. 
I  am,  gnntlomeu,  yonni  tntly, 

ALEXANDbK  UUAHAM  BELL. 


I  11  (liHtllUCII  of 

i'iit*'<l  with  Hh 
iHtuure  of  ttvo 
<liciilikr  to  tht< 
II'  iix'li.  Thti 
rcHciitiition  of 
bullet  livH  l)«- 


AM  HELL. 


m 


